From Two-Partism to Alternating Predominance: The Changing UK Party System, 1950–2010
| Published date | 01 June 2013 |
| DOI | 10.1111/j.1467-9248.2012.00966.x |
| Author | Thomas Quinn |
| Date | 01 June 2013 |
| Subject Matter | Original Article |
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P O L I T I C A L S T U D I E S : 2 0 1 3 VO L 6 1 , 3 7 8 – 4 0 0
doi: 10.1111/j.1467-9248.2012.00966.x
From Two-Partism to Alternating Predominance:
The Changing UK Party System, 1950–2010post_966378..400
Thomas Quinn
University of Essex
This article uses Sartori’s classification of party systems to map changes in the post-war UK party system. Using
measures of the effective number of parties and of parties’ policy positions, the article shows that ‘classic’ two-partism
from 1950 to 1970 broke down amid ideological polarisation. This development created a ‘vacated centre’, which the
Liberals filled, leading to fragmentation of the electoral-party system. This period gave way in 1997 to one in which
ideological convergence returned, alongside further electoral fragmentation. The uneven decline in the vote shares of
the parties finishing first and second led to supermajorities and two long periods of single-party rule from 1979 to
2010. The article argues that the UK had an alternating-predominant party system in this period. This system was a
hybrid of single-party predominance and classic two-partism, in which competition between the two main parties was
usually very weak but where there was some scope for governmental alternation.
Keywords: Britain; party system; two-partism; multipartism; predominant party system
The United Kingdom’s party system was long regarded as one of the classic cases of
two-partism (Duverger, 1954; Sartori, 1976, pp. 185–92). The domination of electoral
politics and alternation in government of the Conservative and Labour parties was one of
the most important characteristics of the ‘Westminster model’ of majoritarian democracy
(Lijphart, 1999). The social basis of two-partism in the post-war period was a cleavage
structure based almost entirely on social class (Denver, 2007, pp. 48–65). Institutionally, the
party system was maintained by the single-member plurality (SMP) electoral system, which
hindered the growth of smaller parties (Duverger, 1954).
In recent years, however, disagreement has grown among political scientists over whether
the two-party label is still applicable to Britain. This development has been a consequence
of the declining combined vote share of Labour and the Conservatives, and the growth of
the Liberal Democrats and the ‘minor’ parties. Although some have continued to argue for
the usefulness of the two-party description (Lynch, 2007; Lynch and Garner, 2005; Ware,
1996), many others have offered different descriptions. These include a multiparty system
(Dunleavy, 2005), a latent moderate plural system ( Webb, 2000, pp. 8–15), a two-and-a-
half-party system (Siaroff, 2003), a two-party-plus system (Heffernan, 2003) and a
predominant-party system (Heywood, 1994; King, 1993).
Although all of these terms capture something important about the UK party system
at various points in time, none is entirely satisfactory. Until the formation of the
Conservative–Liberal Democrat coalition government in 2010, post-war British govern-
ments did indeed alternate between single-party majority Labour and Conservative admin-
istrations, and alternation in office is a defining feature of two-partism. However, alternation
appeared to have broken down for long periods in the 1980s, 1990s and 2000s. Moreover,
the two major parties saw their combined vote share fall from 95 per cent in the 1950s to
© 2012 The Authors. Political Studies © 2012 Political Studies Association
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just 65 per cent by 2010, indicating that the UK was no longer a ‘classic’ case of
two-partism. Other descriptions were similarly problematic. Multipartism was evident in
the electoral arena, but not in the parliamentary arena until 2010, a consequence entirely of
the SMP electoral system. Latent moderate pluralism describes this disjuncture between the
electoral and parliamentary arenas but does not entirely capture that which is manifest and
not merely latent. Two-and-a-half-partism and two-party-plus are largely descriptive catch-
all terms that indicate the presence of two major parties and one or more smaller ones but
reveal little about the structure of party competition. Finally, a predominant-party system
was heralded after the Conservatives’ fourth consecutive election victory in 1992 but five
years later it was swept away in the New Labour landslide.
This proliferation of widely diverging terms is indicative of the uncertainty over how to
characterise Britain’s party system. The absence of consensus partly reflects the difficulty of
capturing the many different and changing features of the British party system in a simple
classification. It may also suggest that there is an imperfect understanding of what the most
important changes have been and how the different elements of the party system relate to
each other.What is needed, therefore, is a theoretically informed and empirically grounded
analysis of the changing nature of the party system.
This article undertakes an analysis of the UK party system between 1950 and 2010
utilising the classificatory schema of Giovanni Sartori (1976). It uses measures of two key
party-system variables – the effective number of parties and ideological distances between
parties – to map changes in the system over time. The article confirms that the era of classic
two-partism from 1950 to 1970 gave way to a system of moderate multipartism in the
electoral arena. However, it did so in distinct phases, with a period of ideological polari-
sation and party-system fragmentation in the 1970s and 1980s followed by a period of
ideological convergence and further fragmentation from 1997 onwards. The article also
shows that the SMP electoral system prevented this fragmentation afflicting the
parliamentary-party system because it functioned as a barrier to entry to the third and
minor parties.
Given the continued allocation of most parliamentary seats to the two major parties, it
is shown that the most important change in the 1980s and after compared with 1950–70
was not the rising support of the Alliance/Liberal Democrats but the wider gap in average
vote shares between the winning party and the runners-up in general elections. This
development, which was a consequence of at least one of the two major parties usually
being discredited for long periods of time from 1979 to 2010, ensured that electoral
fragmentation was uneven and consequently distorted in the parliamentary arena, with an
increased frequency of supermajorities in parliament for one or other main party. The
article argues that the UK party system between 1979 and 2010 should be regarded as one
of alternating predominance, a hybrid of one-party predominance and classic two-partism, in
which both major parties enjoyed lengthy spells of single-party rule. Its defining feature was
prolonged periods of weak competition until the major opposition party was able to
modernise itself sufficiently to be trusted by voters.
The analysis in this article focuses on the party system as a set of (largely competitive)
interactions between political parties. It does not examine in detail changes in voting
behaviour stemming from partisan and class de-alignment. These important issues have
© 2012 The Authors. Political Studies © 2012 Political Studies Association
POLITICAL STUDIES: 2013, 61(2)
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T H O M A S Q U I N N
been addressed elsewhere (e.g. Denver, 2007, pp. 66–93). The distribution of votes is of
course crucial in any study of party systems but it is possible to examine parties’ inter-
actions with each other without a detailed discussion of changing social cleavages. Exten-
sive electoral change can be accompanied by party-system stability and vice versa (Mair,
1997, p. 215). It should also be noted that this article restricts itself to the UK-wide party
system. The regional party systems of Scotland, Wales and Northern Ireland are beyond
its scope.
The article is organised as follows. The first section briefly recounts approaches to the
classification of party systems before setting out Sartori’s method. The article then turns
to the UK, describing shifts in the party system between 1950 and 2010 before pre-
senting data on party fragmentation and ideological distance in order to map these shifts.
After illustrating the disjuncture between the electoral and parliamentary arenas, the
article argues that the party system from the 1980s was an uncompetitive one of alter-
nating predominance.
Classifying Party Systems
Numerous classificatory schemas have been suggested for describing party systems (for an
overview see Ware, 1996, pp. 154–75; see also Mair, 1990, pp. 285–349). The simplest ones
count the number of parties. The major types of system by this criterion are two-party
systems, three-to-five-party systems and more-than-five-party systems. Competition is
most intense in two-party systems because it is zero-sum in nature, whereas competition
and cooperation may characterise party strategies in multiparty systems. More-than-five-
party systems generally have a greater ideological spread than three-to-five-party systems.
In some ‘two-party’ systems there may be more than strictly two parties competing but
their impact on major-party competition is limited, as with the small Liberal party in
Britain in the 1950s. For Sartori, a party is considered relevant if it possesses coalition potential
or blackmail potential; that is, if it has some chance of...
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