Contrary to popular belief, other parties, often referred to as third parties, do exist in the US; but, they typically receive only a tiny fraction of the popular vote.
In the 2008 presidential election Ralph Nadar of the Independent, Peace and Freedom Party received 0.56% of the vote and Libertarian Party nominee Bob Barr received 0.40% of the vote.
Of the 100 seats in the current US Senate, independents hold 2 seats: Joe Lieberman (Connecticut) and Bernie Sanders (Vermont).
In the House of Representatives, none of the 435 seats are held by third parties.
If the election is close, third party candidates can have a substantial impact on the results. Political activist Ralph Nader has been an independent candidate for President of the United States in five elections. In 2000, as the Green Party nominee, Nader received 2,878,000 votes and was widely criticised by liberals for taking votes from Al Gore.
In 1992 businessman Ross Perot ran as an independent candidate for the US presidency under the banner of United We Stand America. He received 19% of the popular vote drawing votes away from both Bill Clinton and George H.W. Bush.
George Washington was the only President who did not represent a political party arguing that the party system was divisive. Washington has also been labeled a Federalist by some.