Two-party system
Third parties, meaning a party other than one of the two dominant parties, are possible in two-party systems, but they are often unlikely to exert much influence by gaining control of legislatures or by winning elections. While there are occasional opinions in the media expressed about the possibility of third parties emerging in the United States, for example, political insiders such as the 1980 presidential candidate John Anderson think the chances of one appearing in the early twenty-first century is remote. A report in "The Guardian" suggested that American politics has been "stuck in a two-way fight between Republicans and Democrats" since the Civil War, and that third-party runs had little meaningful success.
United States presidential primary
There is no provision for the role of political parties in the United States Constitution, since the Founding Fathers did not originally intend for American politics to be partisan. In Federalist Papers No. 9 and No. 10, Alexander Hamilton and James Madison, respectively, wrote specifically about the dangers of domestic political factions. Thus in the first two presidential elections, the Electoral College handled the nominations and elections in 1789 and 1792 that selected George Washington. The beginnings of the American two-party system then emerged from Washington's immediate circle of advisors. Hamilton and Madison, who wrote the aforementioned Federalist Papers against political factions, ended up being the core leaders in this partisanship: Hamilton became the leader of Federalist Party while Madison co-helmed the Democratic-Republican Party with Thomas Jefferson.