Aside from the Democratic Party and the Republican Party, other U.S. political parties are the Libertarian Party, the Green Party and the Constitution Party. The latter three were among a small number of alternative parties that gained ballot access in more than five states for the 2012 U.S. Presidential election.
Since the 95th U.S. Congress convened in 1977, there have been no senators from parties aside from the Democratic or Republican Party, as of 2015. While there have been senators elected as independents, each of these senators has caucused with one of the two major parties. For six years during the 1970s, there was a single third-party member in the Senate representing the Conservative Party of New York. This was the first time since the 79th Congress convened in 1945 that there was a senator representing a third party.