Third party (politics)

In electoral politics, a third party is any party contending for votes that failed to outpoll either of its two strongest rivals (or, in the context of an impending election, is considered highly unlikely to do so). The distinction is particularly significant in two-party systems. In any case "third" is often used figuratively, as in "the third parties", where the intent, literally stated, is "the third and succeeding parties".

For instance, in the United Kingdom a third party is a national political party, other than the Conservatives and Labour, which has at least one member in the House of Commons. Since 2015, it is used for the Scottish National Party. In Scotland the dominant parliamentary party since 2016 has been the Scottish National Party with the Conservative party the next largest party and the Labour party third.

In the United States of America, there have been numerous "third parties". The largest since the mid-20th century are the Libertarian and Green Parties.

The term "third parties" is used mostly in countries with first past the post electoral systems, as those systems tend to create a two-party system, so that successful smaller parties are rare.

Countries using proportional representation give little advantage to the largest two parties, so they tend to elect many parties. Therefore, in those countries, three, four, or more political parties are usually elected to legislatures. In such parliamentary systems, coalitions often include smaller parties; since they may participate in a coalition government, there is not a sharp distinction with a 'major' party. In two-party systems, on the other hand, only the major parties have a serious chance of forming a government. Similarly, in presidential systems, third-party candidates are rarely elected president.

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