In a two-party system a third party is a party other than the two dominant ones. While technically the term is limited to the third largest party, it is often used as shorthand to describe any smaller party. For instance, in the United Kingdom a third party is a national political party other than the Conservatives and Labour which has a substantial presence in the House of Commons. It is currently generally used to refer to the Liberal Democrats.
For the most part third parties exist in countries with first past the post electoral systems as these systems tend to be biased in favour of the two-party system, making successful smaller parties rare. Countries using proportional representation also generally have two dominant parties or coalitions, but there are so many smaller parties that referring to them as third parties makes little sense.
A party needs to have a certain level of success to be designated a third party. Smaller parties that only win a small percentage of the vote and no seats in the legislature are often termed minor or fringe parties. In U.S. politics, for instance, a third party is a political party other than the Democrats or Republicans organized in all or nearly all states.
Third parties are not usually true contenders for forming a government or winning the presidency. There are many reasons for third parties to run however. The platform of a national election campaign means that attention will be paid to the opinions of third parties. The larger parties will be forced to respond and adapt to these challenges, and often the larger parties copy ideas from smaller challengers. Some third parties also hope that the party can slowly build its support and eventually become one of the dominant parties, as the Labour Party in Britain did. In the Westminster system there is also the possibility of minority governments, that can give smaller parties strength disproportional to their size.
The first modern third party is generally considered to be the Irish Parliamentary Party that pushed for Home Rule in Ireland in the late nineteenth century.
- Third party (Canada)
- Third party (United States)