Third-Party Strategy under Plurality Rule: The British Liberal Democrats and the New Zealand Social Credit Party
| Date | 01 October 2017 |
| Author | Thomas Quinn |
| Published date | 01 October 2017 |
| DOI | 10.1177/0032321716677991 |
| Subject Matter | Articles |
677991PSX0010.1177/0032321716677991Political StudiesQuinn
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Political Studies
2017, Vol. 65(3) 740 –763
Third-Party Strategy under
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Liberal Democrats and the New
Zealand Social Credit Party
Thomas Quinn
Abstract
This article examines the strategic options facing small centrist third parties in two-party
parliamentary systems operating under the single-member district plurality electoral system. It
uses a spatial model to show that centrist third parties are better off targeting the ‘safe’ districts
of a major party rather than marginal districts. Furthermore, it is optimal to target one party’s
districts, not both, to benefit from tactical and protest voting. This article also questions the
implicit conclusion of the median-legislator theorem that pivotality-seeking is the best strategy
for a third party, at least under the single-member district plurality system, because that would
usurp voters’ ability to select the executive directly, a key feature of two-partism. Finally, this
article shows that third parties can damage themselves if they ‘flip’ their strategies from opposing
particular major parties to supporting them. Evidence is provided for the British Liberal Democrats
and New Zealand’s historic Social Credit Party.
Keywords
Duverger’s law, plurality electoral system, third parties, Liberal Democrats, Social Credit Party
(New Zealand)
Accepted: 19 September 2016
Centrist third parties have long been a feature of two-party systems based on the single-
member district plurality (SMDP) electoral system, particularly in parliamentary democ-
racies (Gerring, 2005; see also Quinn, 2016). They have been described as ‘safety-valves’
for two-partism (McCraw, 1979: 54), offering dissatisfied voters an alternative to the
major parties (Kang, 1997). Some have secured significant proportions of the vote: the
Liberal Democrats won 17%–25% of the vote in UK general elections between 1983 and
2010, while Social Credit achieved 20% in New Zealand in 1981 (Miller, 1989; Russell
and Fieldhouse, 2005). However, unless third parties have geographically concentrated
Department of Government, University of Essex, Colchester, UK
Corresponding author:
Thomas Quinn, Department of Government, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK.
Email: tquinn@essex.ac.uk
Quinn
741
support, SMDP usually prevents them converting votes proportionately into seats because
of the ‘wasted-vote’ problem (Cox, 1997; Duverger, 1964).
Much of the literature on third parties is country specific, including the UK (Cutts,
2012; MacIver, 1996; Russell et al., 2007), the USA (Rosenstone et al., 1984), New
Zealand (McCraw, 1979) and Canada (Pinard, 1971). However, third-party strategy is
under-developed theoretically. Recent research has yielded important insights, particu-
larly on how third parties motivate major-party divergence (Adams and Merrill, 2006;
Nagel and Wlezien, 2010). Although some of this literature discusses district-level com-
petition, much of it focuses on the national level. Yet votes in SMDP elections are cast in
districts (Cox, 1997). There are variations across districts, with some ‘safe’ for one party,
while others are ‘marginal’ (Johnston and Pattie, 2006). The intensity of competition dif-
fers between districts and so might the identity of the main competitors (Johnston and
Pattie, 2011; Johnston et al., 2012, 2013, 2016).
Building on the work of Maurice Pinard (1971) and Won-Taek Kang (1997) on third
parties, and Gary Cox (1997) on SMDP, this article examines centrist third-party strategy.
It sketches a spatial model of how third parties can become the recognised challenger to
the incumbent in some districts, benefiting from tactical and protest voting. That is most
likely to happen in districts of one-party dominance, where one major party is already
weak. Here, the ‘wasted vote’ logic can work in favour of a third party and against the
weak major party.
This article challenges the view that the optimal strategy for a centrist third party is
pivotality-seeking in a hung parliament, striking deals with whichever party offers it the
best terms (Keman, 1994). It may be better off primarily opposing one major party. This
enables it to attract tactical votes from the supporters of one major party in districts where
the latter is weak, to deprive the other major party of a seat and reduce its chances of
controlling the executive. This strategy preserves voters’ exclusive power to select the
executive. If a third party is willing to deal with either major party, voters are uncertain
what executive they are voting for when they support it, weakening their incentives to do
so. Moreover, third parties can damage themselves by ‘flipping’ from opposition to sup-
port for a major party.
After developing the theory of third-party strategy, this article applies it to the British
Liberal Democrats and New Zealand’s historic Social Credit Party. The parties were
chosen because of their relative centrism, positioned between the two major parties in each
country. The analysis is not applicable without modification to non-centrist third parties.
Third Parties and Plurality Rule
The relationship between SMDP and two-party politics was established in ‘Duverger’s
law’, which states that ‘[a]n almost complete correlation is observable between the simple-
majority single-ballot system and the two-party system’ (Cox, 1997; Duverger, 1964: 217;
Ware, 2009). Two-partism is reinforced by two effects under SMDP. A ‘psychological
effect’ deters voters from ‘wasting’ their votes on candidates with no realistic chance of
winning. A ‘mechanical effect’ of plurality rule is that the need to win in districts leaves
smaller parties under-represented in parliament (Duverger, 1964: 224–226).
SMDP tends to reduce electoral competition to two viable candidates. If the incumbent
leads an electoral race, voters who oppose her will seek to coordinate their opposition
behind the best-placed rival candidate, turning the contest into a two-horse race. In this
‘Duvergerian equilibrium’, there are only two candidates at the district level, with all
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Political Studies 65 (3)
others abandoned by voters fearful of ‘wasting’ their votes (Cox, 1997: 72). Sometimes, it
might not be clear which of two rivals is best placed to defeat the incumbent because the
challengers are evenly matched in support. This may produce what Cox (1997: 72) calls a
‘non-Duvergerian equilibrium’, with two challengers splitting the anti-incumbent vote.
The logic of Duverger’s law is clear at the district level, where voters cast their votes. It
implies that competition reduces to two viable candidates or parties in each district.
However, this does not explain how the same two parties dominate every district in a
national two-party system. Further assumptions are required to derive national two-partism.
According to Cox (1997: 181–202), these concern the competition for executive power. If
executive power is strong, it is highly valued by politicians. If the executive is selected by a
process akin to a plurality election, for example, when the leader of the largest legislative
group gets the first chance to form a government, legislators have incentives to organise into
parties to control the executive. If voters select legislators at the same time as executive
selection occurs, they effectively elect the government directly. These factors produce
national two-partism (Cox, 1997: 190–192).
This article takes national two-partism under SMDP as its starting point and considers
how third parties arise. The focus is on centrist third parties establishing themselves
within the primary cleavage alignment, rather than nationalist parties with geographically
concentrated support benefiting from a secondary cleavage, although the latter can help
third parties.
District-Level One-Party Dominance
The theoretical literature on third parties under SMDP is not extensive, but some impor-
tant ideas have emerged. Maurice Pinard (1971) provided a sociological account of the
success of the Social Credit Party in Quebec in the Canadian federal election of 1962.
He argued that third parties required a ‘grievance’, often economic, to spur their growth
on the back of protest votes. However, they performed better in areas of ‘one-party domi-
nance’ because the weaker major party would be unlikely to win these districts, which
were safe for the other major party (Pinard, 1971: 63–71; see also Johnston et al., 2016;
Johnston and Pattie, 2011).
Building on Pinard, Won-Taek Kang (1997: 40–43) outlined a public-choice model of
third parties under SMDP. He reformulated district-level one-party dominance in spatial
terms, with the distribution of voters’ preferences skewed to one end of the ideological
spectrum. Such districts offer more opportunities for third parties than those in which
both major parties are strong. Kang used an exit-voice-loyalty framework, but while that
is not the present approach, the spatial model is useful and can be supplemented with
Cox’s (1997) interpretation of Duverger.
Assume there are two major parties, Left (L) and Right (R), competing in a large num-
ber of districts under SMDP. The districts can be categorised as strongly L (L’s...
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