Coalition in a Plurality System: Explaining Party System ...
Transcript of Coalition in a Plurality System: Explaining Party System ...
Coalition in a Plurality System:
Explaining Party System Fragmentation in Britain
Jane Green
Ed Fieldhouse
Chris Prosser
University of Manchester
Paper prepared for the UC Berkeley British Politics Group election conference, 2nd September 2015.
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Abstract
Electoral system theories expect proportional systems to enhance minor
party voting and plurality electoral systems to reduce it. This paper
illustrates how the likelihood of coalition government results in incentives
to vote for minor parties in the absence of proportional representation.
We advance a theory of why expectations of coalition government
enhance strategic and sincere voting for minor parties. We demonstrate
support for our theory using analyses of vote choices in the 2015 British
general election. The findings of this paper are important for electoral
system theories. They reveal that so-called proportional electoral system
effects may arise, in part, due to the presence of coalition government
that so often accompanies proportional representation. The findings also
shed light on an important trend in British politics towards the
fragmentation of the party system and a marked increase in this tendency
in the 2015 British general election.
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The 2015 general election result saw the Conservative party win a majority of seats in the House of
Commons after a period of governing in coalition with the Liberal Democrats. At first glance the
result may look like a return to the classic two-party majoritarian government under a plurality
electoral system. But this conclusion would be wrong. 2015 represents a high watermark for votes
for 'other' parties - those parties challenging the traditional establishment parties in Westminster.
Vote shares for UKIP leapt from 3.1% to 12.6%, the Greens from 1.0% to 3.8%, the SNP leapt from
19.9% to 50% in Scotland and Plaid Cymru saw a small increase from 11.3% to 12.1% in Wales. The
two-party vote share increased by only 2.2% despite the spectacular collapse of the well establish
third party the Liberal Democrats, who lost 15% of the vote. The Conservative majority arose not
because of a surge in popular support (the party gained just 0.8% share of the vote) but because of
the more successful Conservative transmission of votes into parliamentary seats, compared to
Labour. In England the Conservative’s vote gain of 1.4% translated into 21 extra seats, whilst
Labour’s 3.6% gain only resulted in 15. Coupled with its collapse in Scotland, this lead to a net loss of
26 seats for Labour, despite increasing its overall vote share by 1.5%.
The 2015 British election raises a theoretically important question, namely, what can account for the
significant rise in minor party votes in 2015 - votes cast under a plurality electoral system expected
to discourage minor party voting? There are many answers to this question that are specific to the
issues and competition characterising the period of British electoral history: the apparent ideological
convergence of the main parties of government, little differentiation in terms of overall appeal for
Labour, the Liberal Democrats or the Conservatives, a strong anti-Westminster sentiment in Scotland
as well as in other parts of the UK, and the salience of cross-cutting issues (e.g. immigration). In this
paper we diverge from those contemporaneous explanations to offer a theory about the influence of
institutions. Namely, we argue that the experience of coalition government - and the expectation of
coalition government - altered the incentives of voters in a way akin to the apparent incentives
under a proportional representation electoral system. The implication of this argument is that
proportional electoral system is not solely responsible for increasing incentives for minor party
voting under proportional systems. It is the outcome of proportional system - coalition government -
that in part leads to the fragmentation of vote choices spread among a greater number of political
parties, not just the transmission of votes to seats. The British case provides a unique test of this
theory about incentives under different institutional contexts. It allows variation in the governing
system, and perceptions thereof, while holding the electoral system constant, thus moving us
towards the ability to isolate these two institutional effects.
Anticipating different coalition likelihoods, how a local vote might increase the chances of a desired
local and national outcome, knowing which policy combinations different parties may adopt - and
whether they would be able to do so, all introduces a great deal of complexity and uncertainty into
the vote calculus (Hobolt and Karp 2010). This is likely to be especially complex and uncertain in
countries that have recently moved to a proportional system (for example, for Scottish elections to
the Scottish parliament, see Carman and Johns 2010) and where coalition combinations are more
unpredictable, in closely fought elections or where parties might join coalitions with different
ideological alternatives. The 2015 British general election was an extreme case in point. Most Britons
had their first experience of coalition in 2010 but were not operating in an electoral system that was
thought to make them likely. The election campaign was filled with speculation and uncertainty
about the outcome but with a consensus that Labour would be the largest party without an overall
majority. There was a significant surge in SNP support in Scotland which led to a late declared denial
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of a Lab-SNP coalition partnership (which many did not believe) and a greater chance of Labour not
winning a majority. There was speculation over the rise of minor parties such as UKIP, and whether
that would translate into seats, and a declaration by the Liberal Democrats that they would partner
with either major party which had a mandate of the largest number of seats. At the constituency
level, unprecedented churn between 2010 and 2015 made normal assumptions of likely winners less
predictable. In short, this was a highly complex and uncertain election. We therefore ask, if voters
anticipated the hung parliament in 2015, what impact did it have?
Our theory of coalition incentives proposes that coalition government increases the incentives to
vote in ways typically expected under proportional electoral systems. We outline new reasons in
support of this expectation with respect to increasing sincere voting for minor parties, and three
reasons with respect to increasing strategic voting for minor parties drawing on the literature on
coalition voting considerations within proportional electoral systems. We reveal how those strategic
voting expectations relate only to coalitions, not to proportional systems per se. Our sincere voting
incentives relate to a reduction in the degree to which a minor party vote is wasted (because a voter
may wish to signal greater popular support to bolster its mandate in coalition, and because the party
has a greater chance of legislative influence in coalition) and an increase in the degree to which a
major party vote (because a major party cannot deliver its full platform, and ideological blurring
reduces incentives to vote strategically and increases incentives to vote expressively).
The expectation of coalition should not always increase the incentives to vote for minor parties,
however. There is one specific context in which existing theory would expect coalition, or its
expectation, to turn voters back towards a major party, as predicted by Duverger (1954); classic
plurality strategic voting for major parties. It is common in countries where the experience of
coalition government is the norm for voters to choose a party within a party bloc; their preferred
choice-set. If a voter expects a party to govern with ideologically proximate parties, it makes sense
for a voter to choose one of those preferred bloc parties that has the greatest likelihood of winning
in their electoral district, or constituency. For some voters this strategic decision will mean a vote for
a minor party. But for other voters it will mean a vote for a major party - specifically where a major
party has the greatest chance of defeating a less ideologically preferred rival. We currently find no
concrete support for this effect in the 2015 British general election, though we do not rule it out.
In addition to making an argument about electoral systems and strategic voting, this paper brings a
new perspective to bear on the outcome of the 2015 British general election. It suggests that the
Conservative party won in spite of coalition-based incentives to vote against the two largest
Westminster parties. And as we show in this paper, it won in part because of the contextual
dependencies of our theory played out in different constituency contexts.
Coalitions in Plurality Systems: How Might Voters Respond?
Voter decisions in different electoral systems have been thought to exhibit strategic voting under
plurality systems, sincere voting under proportional systems (Duverger 1954; Cox 1997), and latterly
strategic voting under proportional systems also, under conditions of low district magnitude, where
the transfer of votes is less proportional and hence votes might be wasted, as in plurality systems
(Leys 1959; Sartori 1968; Cox and Shugart 1996; Cox 1997). Sincere voting refers to voting simply for
one's preferred party, strategic (or tactical) voting to an instrumentally motivated vote choice for a
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party that has a better chance of influencing government policy than a favoured party (McKelvey
and Ordeshook 1972; Cox and Shugart 1996; Cox 1997; Alvarez and Nagler 2000).
Recent research has begun to illuminate how voters respond to the prospect of coalitions, naturally
exploring this decision-calculus in a proportional system context; where coalition governments arise.
Voting can be strategic in these proportional systems where voters attempt to maximize a preferred
policy outcome by calculating the chances of electing a coalition with policies closest to their
preference, and voting accordingly. Hence, there are two reasons to vote strategically under a
proportional system; one if the transfer of votes is less proportional, where there is low district
magnitude (the number of seats per district), and another where voters vote strategically to
maximize the chances of different coalition outcomes.
Hobolt and Karp (2010) distinguish between three types of policy-maximizing strategic voting in
proportional representation systems. The first is voting as a 'threshold insurance policy'. Voters
increase the likelihood of a preferred coalition by voting for a minor coalition partner rather than
their preferred party, if they think the minor party may be in danger of not getting enough votes to
pass an electoral threshold. This threshold effect has been found in German elections (Gschwend
2007; Shikano et al. 2009) where there is a formal threshold, but the effect could work in any system
in which a preferred coalition can only be formed where a minor party gets 'enough' votes or seats.
The second type is known as 'coalition-targeted Duvergerian voting' (Bargsted and Kedar, 2009). If a
voter's preferred party is unlikely to be part of the governing coalition, voters opt for a second
preference option among those parties likely to be coalition partners. This kind of second preference
voting is similar to strategic voting in plurality systems where a vote for a sincere preference will
result in that vote being 'wasted'. The third kind of policy-maximizing strategic voting is voting as a
'balancing strategy'. Voters opt for a party which, if in the coalition, will move the coalition closer to
their preferred position (Kedar 2005a; 2005b; Austen-Smith and Banks 1988). Note that this
balancing requires that a voter believes their preferred party may be moved away from their own
position (for example, through watering down of policy under coalition negotiations) by another
potential coalition partner.
In our view, neither 'threshold insurance policy' voting, 'coalition-targeted Duvergerian voting' nor
'balancing strategy' voting need be unique to proportional systems. Each of these types of policy-
maximizing strategic voting could also occur in plurality systems if the voter believes a coalition
government is likely. Indeed, given the likelihood of strategic voting under plurality systems, relative
to proportional systems, we expect that in a system that incentivizes strategic voting and where a
coalition is expected, these types of policy-maximizing strategic votes may be especially important.
Note, however, that strategic voting in plurality systems is supposed to favour two-partyism
(Duverger 1954). If coalition expectations are coupled with a plurality system, then coalition-based
policy-maximizing strategic voting might favour multi-partyism in a plurality system. That is to say,
voters may have incentives to vote in ways in plurality systems thought to be consistent with
proportional systems, but both kinds of strategic voting are associated with the common outcomes
of those systems - coalitions - rather than with the electoral systems per se.
The British case study is central to our thinking. The British plurality system delivered the first
coalition government in 2010 since the post-war period, and the first formal five-year coalition in the
majority of British voters' experiences. Not only was this the first experience of coalition, but many
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voters expected the outcome of the 2015 British general election to result in another period of
coalition. This expectation increased significantly throughout the election campaign as the rhetoric,
strategies and the polls all focused on an outcome where neither main party would win a majority.
The result, despite delivering a surprise victory for the Conservatives, also resulted in the largest
ever vote shares gained by minor parties in any British general election. Despite the collapse of the
Liberal Democrat's vote between 2010 and 2015, the two party share increased by only 2.3 points. In
total, the support for minor parties (not including the Liberal Democrats) increased from 9.8% to
22.9% between 2010 and 2015, as shown in the blue line in Figure 1. The Green line is the share for
others if the Liberal Democrats are included in this category. Figure 1 reveals how the 2015 followed
a trend of increasing support for minor parties, but that it also demonstrates a very significant level
change in this trend.
Figure 1 about here
How could a plurality system, thought to lead to strategic desertion of minor parties, result in a
surge in minor party support? Duverger (1954) expected plurality systems to lead to two-partyism
because a voter who might otherwise cast a sincere vote for a minor party would see their vote
wasted. Instead, strategic desertion of minor parties will result in the voter choosing their second (or
third) preference between potential winning parties. Here we argue for the impact of coalition
government increasing sincere voting and strategic voting for minor parties, irrespective of the
electoral system. Since the Liberal Democrats are not one of the two major parties, and they are
expected to be penalised by the plurality system via strategic desertion, we classify the Liberal
Democrats as a minor party in our theory and analysis. To the three types of policy-maximizing
strategic voting listed above - which are not unique to minor parties but which are highly relevant to
their support (especially threshold insurance policy voting) - we add additional coalition
considerations and incentives specific to enhancing sincere voting for minor parties. These incentives
are not unique to plurality systems or indeed to proportional systems. We propose additions to the
emerging literature on coalition voting incentives, most usually analysed under proportionality.
Coalition Enhances Strategic Voting for Minor Parties
'Threshold insurance policy' voting relates specifically to parties that may not get over an electoral
threshold; therefore to minor parties. According to this view of coalition policy-maximizing strategic
voting, a minor party may be supported rather than a preferred party to ensure a preferred
coalition. And as noted above, the logic of this expectation need not be restricted to formal
thresholds but to any situation in which a voter opts to increase the chance of a favoured coalition
by ensuring a minor party is elected. And as also noted above, this logic need not be restricted to
proportional electoral systems. Thus, given the prospects of coalition, a voter may vote strategically
for a minor party to ensure that party joins a coalition with the voter's preferred party.
'Coalition-targeted Duvergerian voting' will result in strategic voting for a second preference minor
party if that minor party has a greater chance of being part of the coalition than the voter's
preferred party. This is made more likely under coalition since coalition enhances the chance a minor
party can form part of any government.
A 'balancing strategy' will lead to greater minor party voting in the event that a voter believes their
preferred party's policies will be altered by a different coalition formation. For example, this
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explanation could apply to Conservatives who vote UKIP to prevent their party from becoming too
moderate in a coalition with the Liberal Democrats, or to Labour supporters who vote SNP in
Scotland to encourage a more pro-austerity Labour party government than if Labour went into
coalition with the Lib Dems. Alternatively, a moderate Conservative could vote Lib Dem to stop their
party being too right-wing, or a Labour voter could vote Lib Dem for the opposite reason.
Each of these incentives could enhance strategic voting for minor parties (i.e. when a voter prefers
another party but votes for a minor party instead), and all are theorised in the presence of coalition
expectations, not in the presence of proportional electoral systems per se.
Coalition Enhances Sincere Voting for Minor Parties
There are additional reasons, we believe, to expect coalition will also enhance sincere voting for
minor parties. That is, the decision to vote for a voter's first minor party preference, rather than to
vote for a major party alternative.
Voters may be more likely to vote sincerely for a minor party if the incentives to vote strategically for
major parties are reduced. This suggests that the presence of coalition may reduce the Duvergerian
incentives of plurality systems. Duverger (1954) expects strategic voting to favour major parties
because a) a vote for a minor party is wasted in plurality systems; and b) voters have incentives to
choose between alternative governments. Coalition alters these incentives.
There are fewer wasted minor party votes under coalition for two reasons. The first is that a minor
party may have greater influence within a coalition government the greater their popular support,
irrespective of where that vote is distributed. Voting for a minor party may offer a different utility
gain for a voter who thinks their preferred party has a chance of being in coalition. The second is
that, whilst the electoral system will still be a barrier to that party winning in a constituency, if the
voter believes the party has a chance of winning locally, the party has a much greater chance under
coalition of having an influence in the legislature. A voter policy-maximizes by voting sincerely.
Conversely, a major party vote might be more wasted under coalition. If a voter strategically deserts
from a minor party in favour of a major party, they do so because that major party is closer to the
voter's preferred policy position than the alternative. But the policy compromise inherent in
coalition negotiations, and the uncertainty regarding which party will form a government when
coalition is more likely (when the race is relatively close) both diminish the incentive to vote
strategically for a major party second preference when a voter expects a coalition.
One further incentive to vote sincerely for a minor party arises when voters face an ambiguous
choice between potential major parties in government. If coalition enhances uncertainty and
ideological blurring between the likely policy platforms of any major party, minor party voters may
be more likely to vote sincerely and expressively, choosing to use their vote as an expression of their
policy beliefs in the context of unclear policy differences between major parties.
Coalition Enhances Plurality Electoral Incentives
Finally, whilst we have highlighted reasons that coalition expectations will increase sincere and
strategic voting for minor parties, even within a plurality system, we do not argue that there are no
'traditional' plurality system effects for some voters, namely, an incentive to increase strategic
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desertion from minor parties in favour of major parties. These incentives still exist, although they
should be less important. Furthermore, for voters anticipating a coalition outcome they least prefer,
we expect people whose first preference is for minor parties to strategically opt for a major second
preference party. Note that the likelihood of coalition can therefore also enhance the impact of
strategic voting for major parties within a plurality system as voters choose a second preference
within their ideological bloc. This expectation is particularly pertinent in an election in which many
commentators believe that the 'threat' of SNP influence in a Labour-led coalition led many voters to
strategically support the Conservatives. If we are to argue that coalition increases support for minor
parties, we need also to weigh up the relative influence of an effect in the opposite direction.
Hypotheses
Coalition hypothesis:
Expectations of a coalition government increases support for minor parties and decreases
support for major parties
Strategic voting hypothesis:
Expectations of a coalition government increases votes for minor parties among existing major
party supporters
Sincere voting hypothesis:
Expectations of coalition government increases votes for minor parties among existing minor
party supporters
Plurality Duvergerian hypothesis:
Expectations of coalition government increases support for major parties and decreases
support for minor parties when a least preferred party may win locally.
Data and Methods
The dependent variables in our analyses are reported vote using the post election wave of the BES
internet panel for each of the major (Conservatives and Labour) and minor parties (UKIP and Greens
in England, SNP in Scotland and Plaid Cymru in Wales).
Our main explanatory variable measures respondents' perceptions of a likely hung parliament, which
denotes whether a coalition government was considered likely. We calculate this variable from
responses to two questions in the BES internet panel; " How likely do you think it is that the
Conservative | Labour party will form a government on its own", each measured on a 0-10 scale
where 0 = very unlikely and 10 = very likely. We then take the mean of each respondent’s answer to
each question and invert the scale, resulting in a variable that ranges from 0 when respondents think
a hung parliament is completely unlikely (both parties are very likely to form a government on their
own) to 10 when a hung parliament is a near certainty (both parties are very unlikely to form
government on their own). We examine the effects both of the expectation of a hung parliament
before the election campaign (in the pre-election wave of the BES internet panel), and whether
respondents thought a hung parliament was more likely (measured as the absolute change in
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likelihood) between the pre-election wave (4) and the campaign wave (5) of the BES internet panel.
The campaign wave randomised survey responses throughout the 38 days of the election campaign.
Our models control for those factors likely to be correlated with coalition expectations and
underlying predisposition to vote for each party; respondent age, their level of interest in the
election, and their like scores for each of the parties (all measured pre-election). The BES internet
panel used a split-sample design asking like-dislike scores for each of the parties (on a 0-10 scale
where 0 = strongly dislike and 10 = strongly like) and 'propensity to vote' questions, asking: 'How
likely is it that you would ever for X party' (0 = very unlikely, 10 = very likely). In order to maximize
the samples, and also following our analyses finding these questions to be functionally equivalent,
these two questions were combined. They allow us to control for partisan bias in coalition
expectations.
The analyses assess whether coalition expectations lead to greater minor party voting (our coalition
hypothesis) using an alternative-specific conditional logit model using our full sample of English
voters. Here we model Liberal Democrat, UKIP, Green, Labour and Conservative vote choice, and
exclude Scotland and Wales as the different choice sets would violate the independence of
irrelevant alternatives assumption of the model. We test two potential causal mechanisms; whether
respondents thought the party had a chance of winning locally, and whether the respondent
thought the party would have influence in the UK government. These mechanisms could increase
strategic voting, but also sincere voting. These are alternative specific variables, alongside party like-
dislike/PTVs. Chance of winning locally was measured in the campaign wave of the survey by a
question which asked ‘How likely is it that each of these parties will win the General Election in your
local constituency?’ Measured on a 0-100 scale for each party. Chance of being in government was
measured by recoding respondent’s answers to ‘Which of these parties do you think has no real
chance of being part of the next UK government (either forming a government by itself or as part of
a coalition)?‘ The variable is coded 1 when a respondent thought a party had a chance of being part
of the next UK government. Choice specific variables are age, election interest, pre-election
expectations of coalition, and change in expectations.
We then assess the effects of coalition expectations upon strategic voting in favour of minor parties.
To do this, we operationalise strategic voting as a minor party vote among respondents whose most
preferred party (measured on the like and propensity to vote scales) is either of the major parties,
Labour or Conservative, excluding those who have a tied preference for the minor party under
examination. Those who did not have a candidate of the minor party in question running in their
constituency are excluded from the analysis. Using stratified logit models, we examine whether
coalition expectations, and change in coalition expectations, increased the likelihood of strategic
defection from the major to each of the minor parties. We also estimate the effects of perceptions
of the likelihood of winning locally and the chance of being part of the UK government upon this
strategic major to minor party desertion, and we add controls.
We assess the effects of coalition expectations upon sincere voting for minor parties by
operationalising sincere voting as a minor party vote among respondents whose most preferred
party (measured on the like and propensity to vote scales) is the minor party in question, including
those who have a tied preference for another party (each model for each party in turn). Again, those
who did not have a candidate of the minor party in question running in their constituency are
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excluded from the analysis. We examine the effects as listed for the stratified strategic voting
models: coalition expectations, change in coalition expectations, likelihood of winning locally and
chance of being part of the UK government.
Finally, we examine whether the 2015 British general election gives support to the classic
Duvergerian expectation (of strategic defection from minor parties to major parties) under an
additional context; whether the respondent thought a rival party had a chance of winning in the
constituency. This is estimated using the stratified models for those who most prefer a minor party
and using a measure of the closeness of the local constituency race between Labour and the
Conservatives, calculated as the absolute difference between how likely a respondent thought each
of the Conservative and Labour candidates were to win in their constituency. This closeness of race
measure is then interacted with expectation of coalition government.
Results
Table 1 presents our tests of the 'Coalition Hypothesis', namely that expectations of coalition will
increase votes for minor parties at the expense of major parties. We also explore the evidence for
two mechanisms; whether respondents believe a party will win in the constituency, and whether
they believe the party has a chance of influencing policy (being part of the government). Both should
increase the incentives to vote for any party. The first rows of Table 1 support those expectations.
Controlling for the strength of feeling towards a party, the belief that party will win locally and the
belief the party will become part of the government has a significant effect on increasing its votes.
The choice-specific models provide the results for expectations of coalition, and changing
expectations of coalition. In each of the minor party reported vote outcomes (Liberal Democrat,
UKIP or Green, in relation to voting Conservative), we find a significant and positive effect of
coalition expectations, as well as a significant and positive effect of an increase in the expectation
that there would be a hung parliament after the election result of May 7th. Table 1 also reveals an
effect of coalition expectations upon a vote for Labour rather than Conservative.
Table 1 about here
These results support our coalition hypothesis. They denote an effect of coalition expectations
within a plurality system, and an effect which increases minor party voting, as we theorised.
Furthermore, across each of our party choices, there is support for the expectation that voters are
more likely to support each party if they think the party can win, and have a chance of being part of
the government. That is to say, it is the perception of likely influence, controlling for the attachment
a respondent feels towards a party, which has a significant effect upon vote choice.
Strategic Voting Hypothesis
If our strategic voting hypothesis is correct, coalition expectations should lead to a greater likelihood
of a strategic vote for a supporter of a major party, in contrast to the usual plurality expectation of
strategic desertion away from minor party voters to major party voters. Table 2 presents the results
of our stratified logit models for each of the minor parties. These models estimate the effects of
coalition expectations for those respondents whose most preferred party is one of the major parties.
It reveals significant and positive effects, as hypothesised, for four out of five of the minor parties
(for the Liberal Democrats, UKIP, Greens and Plaid Cymru), and no significant effects for the SNP. In
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the Liberal Democrat, UKIP and Green party models we find significant effects for coalition
expectations and for changes in coalition expectations, and for Plaid Cymru for change only.
Table 2 about here
The following Figure 2 presents the predicted probability of voting for each of the minor parties
(among major party preferers). Note the Y axis ranges from 0.00 to 0.15.
Figure 2 about here
In addition to the main effects reported in Table 2, we find support for our mechanisms, namely, the
likelihood each party will win in the constituency (significant in the Liberal Democrat, UKIP and
Green models), and the chance the party will be part of the UK government (in the Liberal Democrat,
UKIP, Green and Plaid Cymru models). It is interesting that neither explanation holds for the SNP,
suggesting that desertion to this party was not motivated strategically but via other explanations. It
is notable that we do not find an effect for the SNP in the opposite direction given the political
climate in 2015; that is, we do not find a negative effect of the expectation that the SNP would be
part of the UK government, or whether the party would win locally, on the decision to vote for a
major party rather than the SNP.
Sincere Voting Hypothesis
If we find support for our sincere voting hypothesis, we should find significant effects of coalition
expectations on votes for minor parties among respondents whose most preferred party is the
minor party in question. Table 3 presents the results of the stratified logit models for each party,
respectively. The results confirm our expectations. There is a positive and statistically significant
effect of coalition expectations before the election for each of the minor party models: for the
Liberal Democrats, UKIP, the Greens, SNP and for Plaid Cymru. There are also additional effects for
changes in expectations in the expected direction for the Liberal Democrats, UKIP and Plaid Cymru.
Table 3 about here
It is interesting that the newly theorised sincere voting incentives appear to be somewhat stronger
in the 2015 UK general election than our results for strategic minor party voting. Figure 3 presents
the predicted probabilities of voting for each of the minor parties by coalition expectations. The y
axis, ranging from 0 to 1, reveals much stronger effects than we observed in Figure 2.
Figure 3 about here
Table 3, above, also provides further support for the expected mechanisms. We find significant
effects of expectations the party will win locally in each of the party models, and significant effects
for the expected change of being part of the UK government for the Liberal Democrats, UKIP and the
Greens, controlling for the strength of feeling to each of the parties, respectively.
Plurality Duvergerian Hypothesis
Finally, we test the reverse expectation to our theory, namely the classic Duvergerian prediction that
minor party supporters will defect strategically to major parties in a plurality system. Given the
findings above, we examine whether this occurs within a certain context - namely, when the
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respondent thinks a rival party may win. We estimate this context by the perceived closeness of the
local race, and interacting whether a hung parliament also made it less likely that a respondent
would vote for a minor party when they perceived this 'threat'. For example, were voters more likely
to vote Conservative rather than for a minor party if they thought Labour could win in their
constituency and they thought there could be a coalition? Or were respondents more likely to vote
Labour rather than Green if they thought the Conservatives could win locally and defeat a Labour
candidate (or a Labour candidate could beat a Conservative) under coalition expectations?
The results in Table 4 provide little support for this classic plurality expectation. For most
respondents, the perception of a close race between the two major parties had no effect on their
vote intention. The exception to this were Green Party supporters, for whom the effects of hung
parliament expectations were diminished when they perceived a close race between Labour and the
Conservatives, as illustrated in figure 4.
Table 4 about here
Figure 4 about here
The tests of the Duvergian plurality hypothesis lend further weight to our coalition, strategic voting
and sincere voting hypotheses of increased support for minor parties, since there appears to be
almost no statistical effect of a classic plurality prediction in the opposite direction. In additional
checks for the plurality expectation, and in light of the widely held view that the SNP threat in 2015
handed a victory to the Conservatives, we also modelled whether respondents thought the SNP
could a) have a chance of being part of the UK government, and b) whether respondents disliked the
SNP. These results strengthened the effects for coalition expectations, supporting our coalition,
strategic and sincere voting hypotheses. We found some potential effects of an SNP threat causing
major parties to pick up more votes, but the results were inconclusive. We intend to explore this
further. Another future next step might be to model the likelihood of winning, either locally or
nationally, of a respondents' least preferred party.
Conclusions
We argued that one of the reasons the UK's 2015 general election delivered a step-change in votes
for minor parties is because the 2015 general election was fought in a new context of expectations
of coalition. Our theory of coalition effects predicted that coalition would increase strategic
incentives to vote for minor parties, and would also increase incentives to vote sincerely. These
expectations go against the grain of classic plurality electoral system predictions (Duverger 1954)
which expect minor parties to lose votes due to strategic desertion in favour of major parties, thus
delivering a two-party system, and they also go against the grain of much commentary of the 2015
British general election. There was a great deal of speculation that the likelihood of a hung
parliament - not least an incorrect likelihood of a hung parliament (due to the errors in the opinion
polls which led to an over-estimation of Labour's support and an under-estimation of the
Conservatives') - led voters to support the Conservatives. Our findings challenge both assumptions.
We find that coalition expectations increased the strategic incentives to vote for minor parties, and
they increased the incentives to vote sincerely for minor parties. Whereas the existing literature has
predicted that coalitions would increase strategic voting (Austen-Smith and Banks 1988; Kedar
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2005a; 2005b; Gschwend 2007; Bargsted and Kedar, 2009; Shikano et al. 2009; Hobolt and Karp
2010), they have neither (a) specified those incentives in relation to minor parties, (b) identified that
those incentives could occur in a plurality electoral system as well as under proportional
representation, or (c) considered in any way the effects of coalition upon sincere voting.
Our theory of coalition-induced sincere and strategic voting for minor parties offers three novel
features. First, we add sincere voting incentives to the existing literature pointing to strategic voting
incentives. Second, we argue that none of these incentives need be specific to proportional systems.
This means that those assumptions of the effects of proportionality are effects of the institutions
that arise from proportionality; coalition, rather than from proportionality per se. The third is we
explicitly reveal how incentives arise at the local level and at a national level. This is perhaps implied
in analyses of strategic voting under coalitions, but it has not been stated or tested directly. Our
theory illuminates how the combination of the national level context and the local level context
work to alter voting incentives under the prospects of coalition.
This paper also has important implications for how we understand and interpret the 2015 British
general election and the rising support for minor parties. An interesting paradox emerges. In an
election in which the expectation of a hung parliament was so important, the election resulted in an
unexpected single-party government. Whether this surprise outcome causes voters in future to off-
set their expectations in their voting considerations can only be speculated about. It is certainly the
case that while the UK has delivered a single-party government against prior expectations, the rise in
voting for minor parties continues to contribute to the conditions making coalitions more likely.
14
Bibliography
Alvarez, R. M. and J. Nagler (2000). "A new approach for modelling strategic voting in multiparty elections." British Journal of Political Science 30(01): 57-75. Armstrong Ii, D. A. and R. M. Duch (2010). "Why can voters anticipate post-election coalition formation likelihoods?" Electoral Studies 29(3): 308-315. Austen-Smith, D. and J. Banks (1988). "Elections, coalitions, and legislative outcomes." American Political Science Review 82(02): 405-422. Bargsted, M. A. and O. Kedar (2009). "Coalition‐targeted Duvergerian voting: how expectations affect voter choice under proportional representation." American Journal of Political Science 53(2): 307-323. Bowler, S., et al. (2010). "Strategic coalition voting: Evidence from New Zealand." Electoral Studies 29(3): 350-357. Carman, C. J. and R. Johns (2010). "Linking coalition attitudes and split-ticket voting: The Scottish Parliament elections of 2007." Electoral Studies 29(3): 381-391. Cox, G. W. (1997). Making votes count: strategic coordination in the world's electoral systems, Cambridge Univ Press. Cox, G. W. (1997). Making votes count: strategic coordination in the world's electoral systems, Cambridge Univ Press. Cox, G. W. and M. S. Shugart (1996). "Strategic voting under proportional representation." Journal of Law, Economics, and Organization 12(2): 299-324. Duverger, M. (1959). Political parties: Their organization and activity in the modern state, Methuen. Fisher, S. D. and S. B. Hobolt (2010). "Coalition government and electoral accountability." Electoral Studies 29(3): 358-369. Gschwend, T. (2007). "Ticket‐splitting and strategic voting under mixed electoral rules: Evidence from Germany." European Journal of Political Research 46(1): 1-23. Hobolt, S. B. and J. A. Karp (2010). "Voters and coalition governments." Electoral Studies 29(3): 299-307. Kedar, O. (2005). "How diffusion of power in parliaments affects voter choice." Political Analysis 13(4): 410-429. Kedar, O. (2005). "When moderate voters prefer extreme parties: Policy balancingin parliamentary elections." American Political Science Review 99(02): 185-199. Leys, C. (1959). "Models, theories, and the theory of political parties." Political Studies 7(2): 127-146. McCuen, B. and R. B. Morton (2010). "Tactical coalition voting and information in the laboratory." Electoral Studies 29(3): 316-328.
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McKelvey, R. D. and P. C. Ordeshook (1972). "A general theory of the calculus of voting." Mathematical applications in political science 6: 32-78. Meffert, M. F. and T. Gschwend (2010). "Strategic coalition voting: Evidence from Austria." Electoral Studies 29(3): 339-349. Powell, G. B. (2000). Elections as instruments of democracy: Majoritarian and proportional visions, Yale University Press. Shikano, S., et al. (2009). "Strategic voting under proportional representation: threshold insurance in German elections." West European Politics 32(3): 634-656.
16
Figures
Figure 1: Vote shares for minor parties, 1945-2015
0
5
10
15
20
25
1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Other Vote Share Other Seat Share
17
Figure 2: Stratified Vote Choice by Hung Parliament Expectation among Major Party Supporters
18
Figure 3: Stratified Vote Choice by Hung Parliament Expectation among Minor Party Supporters
19
Figure 4: Predicted Probabilities of Voting Green by closeness of race and coalition expectations
20
Tables
Table 1: Alternative-Specific Logit Model of 2015 Vote Choice
Party Like/PTV 2.082***
(0.0265)
Win Constituency W5 0.0145***
(0.000587)
Chance Government 0.321***
(0.0609)
Labour Hung Parliament Expectation W4 0.0731***
(0.0215)
Hung Parliament Expectation Change -0.00328
(0.0175)
Age -0.00965***
(0.00236)
Election Interest 0.0792
(0.0515)
Constant -0.140
(0.222)
Liberal Democrat Hung Parliament Expectation W4 0.184***
(0.0253)
Hung Parliament Expectation Change 0.0524**
(0.0208)
Age -0.00235
(0.00275)
Election Interest 0.140**
(0.0619)
Constant -2.725***
(0.271)
UKIP Hung Parliament Expectation W4 0.125***
(0.0221)
Hung Parliament Expectation Change 0.0486***
(0.0175)
Age 0.00206
(0.00273)
Election Interest -0.00616
(0.0536)
Constant -1.994***
(0.246)
Green Party Hung Parliament Expectation W4 0.165***
(0.0310)
Hung Parliament Expectation Change 0.0724***
(0.0264)
Age -0.0230***
(0.00347)
Election Interest 0.168**
(0.0787)
Constant -2.017***
(0.338)
Observations 67202
Cases 13905
Statistical significance: * p<0.05, ** p<0.01, *** p<0.001
21
Table 2: Model of Minor Party Voting in 2015 among Major Party Supporters
Liberal
Democrats UKIP Green Party SNP Plaid Cymru
Hung Parliament Expectation W4 0.182*** 0.174*** 0.101* -0.110 0.141
(0.0285) (0.0400) (0.0573) (0.0782) (0.124)
Hung Parliament Expectation Change 0.0944*** 0.103*** 0.0934** 0.0826 0.233***
(0.0230) (0.0309) (0.0465) (0.0599) (0.0859)
Win Constituency W5 0.0330*** 0.0108*** 0.0128*** -0.000688 0.00978
(0.00177) (0.00276) (0.00426) (0.00510) (0.00663)
Party Like/PTV 0.770*** 1.410*** 1.126*** 1.861*** 0.370
(0.0589) (0.0958) (0.130) (0.196) (0.237)
Age 0.00114 0.00835* -0.0202*** -0.00957 -0.0179
(0.00303) (0.00471) (0.00588) (0.00862) (0.0129)
Election interest 0.0659 -0.479*** -0.0918 -0.459** -0.584**
(0.0803) (0.0948) (0.154) (0.184) (0.268)
Chance Government 0.407** 0.455*** 0.522*** 0.0277 1.102***
(0.163) (0.165) (0.202) (0.359) (0.419)
Constant -6.249*** -4.579*** -4.432*** 0.703 -2.447*
(0.387) (0.467) (0.673) (0.875) (1.277)
N 11755 11075 10173 1405 1018
Pseudo R2 0.1697 0.1814 0.1310 0.2247 0.1156
Statistical significance: * p<0.1, ** p<0.05, *** p<0.01
22
Table 3: Model of Minor Party Voting in 2015 among Minor Party Supporters
Liberal
Democrats UKIP Green Party SNP Plaid Cymru
Hung Parliament Expectation W4 0.164*** 0.202*** 0.0916*** 0.216*** 0.441***
(0.0270) (0.0194) (0.0239) (0.0521) (0.0778)
Hung Parliament Expectation Change 0.0557** 0.0789*** 0.00752 0.0657 0.159***
(0.0221) (0.0158) (0.0210) (0.0439) (0.0581)
Win Constituency W5 0.0218*** 0.0115*** 0.00848*** 0.00895** 0.00872**
(0.00176) (0.00145) (0.00196) (0.00416) (0.00442)
Party Like/PTV 0.605*** 0.984*** 0.754*** 2.468*** 0.840***
(0.0714) (0.0713) (0.0740) (0.226) (0.217)
Age 0.00906*** 0.00568** -0.0152*** -0.0145** -0.0105
(0.00299) (0.00269) (0.00283) (0.00651) (0.00928)
Election interest 0.152** 0.0204 0.0134 -0.0195 0.516**
(0.0682) (0.0526) (0.0688) (0.148) (0.208)
Chance Government 0.462** 0.590*** 0.458*** 0.347 0.449
(0.187) (0.0974) (0.0947) (0.283) (0.280)
Constant -4.241*** -3.830*** -2.338*** -1.219* -5.747***
(0.346) (0.264) (0.295) (0.680) (1.037)
N 2198 3572 2707 1687 329
Pseudo R2 0.1209 0.1120 0.0809 0.2005 0.1845
Statistical significance: * p<0.1, ** p<0.05, *** p<0.01
23
Table 4: Models of Minor Party Voting in 2015 among Minor Party Voters, by Strategic Context
Liberal Democrats UKIP Green Party SNP Plaid Cymru
Hung Parliament Expectation W4 0.173*** 0.190*** 0.000129 0.207** 0.482***
(0.0428) (0.0301) (0.0387) (0.0860) (0.121)
Hung Parliament Expectation Change 0.0415* 0.0803*** -0.00216 0.0649 0.155***
(0.0228) (0.0163) (0.0218) (0.0445) (0.0599)
Win Constituency W5 0.0229*** 0.0120*** 0.00975*** 0.0114*** 0.00883*
(0.00182) (0.00150) (0.00203) (0.00430) (0.00452)
Party Like/PTV 0.594*** 0.985*** 0.729*** 2.384*** 0.834***
(0.0736) (0.0733) (0.0763) (0.229) (0.220)
Age 0.00917*** 0.00559** -0.0135*** -0.0152** -0.0123
(0.00308) (0.00276) (0.00291) (0.00662) (0.00956)
Election interest 0.163** 0.0129 0.00166 0.0274 0.569***
(0.0701) (0.0540) (0.0714) (0.150) (0.217)
Chance Government 0.403** 0.593*** 0.469*** 0.463* 0.398
(0.197) (0.101) (0.0979) (0.281) (0.284)
Local Lab-Con close race 0.0111** -0.00116 -0.00618 -0.00750 0.00598
(0.00471) (0.00322) (0.00413) (0.00995) (0.0124)
Hung Parliament Expectation W4 X -0.000663 0.000319 0.00186*** -0.0000180 -0.000841 Local Lab-Con close race (0.000779) (0.000542) (0.000666) (0.00155) (0.00195) Constant -4.611*** -3.791*** -2.068*** -1.203 -6.080*** (0.402) (0.293) (0.342) (0.772) (1.132)
N 2108 3406 2573 1668 320 Pseudo R
2 0.1306 0.1133 0.0847 0.1961 0.1888
Statistical significance: * p<0.1, ** p<0.05, *** p<0.01