A two-party system is duopolistic in that it is dominated by two ‘major’ parties that have a roughly equal prospect of winning government power. In its classical form, a two-party system can be identified by three criteria: Although a number of ‘minor’ parties may exist, only two parties enjoy sufficient electoral and legislative strength to have a realistic prospect of winning government power.
The larger party is able to rule alone (usually on the basis of a legislative majority); the other provides the opposition. Power alternates between these parties; both are ‘electable’, the opposition serving as a ‘government in the wings’. The UK and the USA are the most frequently cited examples of states with two-party systems, though others have included Canada, Australia and, until the introduction of electoral reform in 1993, New Zealand. Arche typal examples of two-party politics are, nevertheless, rare. The UK, for instance, often portrayed as the model two-party system, has conformed to its three defining criteria only for particular (and, some would argue, untypical) periods of its history. Even the apparent Labour–Conservative two-partyism of the early post-World War II period (power alternating four times between 1945 and 1970) was punctuated by 13 years of continuous Conservative rule (1951–64), a period during which time Labour’s electability was called into question. Moreover, despite persistent major party domination of the House of Commons in the UK, it is more doubtful that a two-party system has existed ‘in the country’ since 1974. This is suggested by the decline of combined Labour–Conservative support (down from over 95 per cent in the early 1950s to consistently below 75 per cent since 1974). Even the seemingly incontrovertible two-partyism of the USA – which, for instance, sees the Republicans and Democrats usually holding between them all the seats in the House of Representatives and the Senate – can be questioned. On the one hand, the presidential system allows one party to capture the White House (the presidency) while the other controls one or both houses of Congress, as, for instance, occurred between 1984 and 2000, meaning that it may not be possible to identify a clear government–opposition divide. On the other hand, ‘third’ party candidates are sometimes of significance. Ross Perot’s 16 per cent of the vote in the 1992 presidential election not only highlighted the decline of the Republican and Democratic parties, but also, arguably, proved decisive in securing victory for Bill Clinton. Two-party politics was once portrayed as the surest way of reconciling responsiveness with the order, representative government with an effective government. Its key advantage is that it makes possible a system of party government, supposedly characterized by stability, choice and accountability. The two major parties are able to offer the electorate a straightforward choice between rival programmes and alternative governments. Voters can support a party knowing that, if it wins the election, it will have the capacity to carry out its manifesto promises without having to negotiate or compromise with coalition partners. This is sometimes seen as one of the attractions of majoritarian electoral systems that exaggerate support for large parties. Two-party systems have also been praised for delivering strong but accountable government based on relentless competition between the governing and opposition parties. Although the government can govern, it can never relax or become complacent because it is constantly confronted by an opposition that acts as a government in waiting. Two-partyism, moreover, creates a bias in favour of moderation, as the two contenders for power, have to battle for ‘floating’ votes in the centre ground. This was, for example, reflected in the so-called ‘social-democratic consensus’ that prevailed in the UK from the 1950s to the 1970s. However, two-party politics and party government have not been so well regarded since the 1970s. Instead of guaranteeing moderation, two-party
systems such as the UK’s have displayed a periodic tendency towards adversary politics . This is reflected in ideological polarization and an emphasis on conflict and argument, rather than consensus and compromise. In the UK in the early 1980s, this was best demonstrated by the movement to the right by a ‘Thatcherized’ Conservative Party and the movement to the left by a radicalized Labour Party, although a new, post-Thatcherite consensus soon emerged. Adversarial two-partyism has often been explained by reference to the class nature of party support (party conflict being seen, ultimately, as a reflection of the class struggle), or as a consequence of party democratization and the influence of ideologically committed grass-roots activists. A further problem with the two-party system is that two evenly-matched parties are encouraged to compete for votes by outdoing each other’s electoral promises, perhaps causing spiralling public spending and fuelling inflation. This amounts to irresponsible party government, in that parties come to power on the basis of election manifestos that they have no capacity to fulfil. A final weakness of two-party systems is the obvious restrictions they impose in terms of electoral and ideological choice. While a choice between just two programmes of government was perhaps sufficient in an era of partisan alignment and class solidarity, it has become quite inadequate in a period of greater individualism and social diversity.