A two-party system is a party system where two major political parties dominate the government. One of the two parties typically holds a majority in the legislature and is usually referred to as the majority or governing party while the other is the minority or opposition party. Around the world, the term has different senses.
For example, in the United States, Jamaica, and Malta, the sense of two-party system describes an arrangement in which all or nearly all elected officials belong to one of the only two major parties, and third parties rarely win any seats in the legislature. In such arrangements, two-party systems are thought to result from various factors like winner-takes-all election rules.
In such systems, while chances for third-party candidates winning election to major national office are remote, it is possible for groups within the larger parties, or in opposition to one or both of them, to exert influence on the two major parties. In contrast, in the United Kingdom and Australia and in other parliamentary systems and elsewhere, the term two-party system is sometimes used to indicate an arrangement in which two major parties dominate elections but in which there are viable third parties which do win seats in the legislature, and in which the two major parties exert proportionately greater influence than their percentage of votes would suggest.
Explanations for why a country with free elections may evolve into a two-party system have been debated. A leading theory, referred to as Duverger’s law, states that two parties are a natural result of a winner-take-all voting system.
There are several reasons why, in some systems, two major parties dominate the political landscape. There has been speculation that a two-party system arose in the United States from early political battling between the federalists and anti-federalists in the first few decades after the ratification of the Constitution, according to several views. In addition, there has been more speculation that the winner-takes-all electoral system as well as particular state and federal laws regarding voting procedures helped to cause a two-party system.
Some historians have suggested that two-party systems promote centrism and encourage political parties to find common positions which appeal to wide swaths of the electorate. In politics, centrism refers to the tendency to avoid political extremes by taking an ideologically intermediate position. It can lead to political stability which leads, in turn, to economic growth. Historian Patrick Allitt of the Teaching Company suggested that it is difficult to overestimate the long term economic benefits of political stability.
Sometimes two-party systems have been seen as preferable to multi-party systems because they are simpler to govern, with less fractiousness and greater harmony, since it discourages radical minor parties, while multi-party systems can sometimes lead to hung parliaments. Italy, with a multi-party system, has had years of divisive politics since 2000, although analyst Silvia Aloisi suggested in 2008 that the nation may be moving closer to a two-party arrangement. The two-party has been identified as simpler since there are fewer voting choices. One analyst suggested the two-party system, in contrast with proportional representation, prevented excessive government interference with economic policy.