Dean Barkley, a key founder of the Minnesota Independence Party, and the only U.S. Senator in the last 60 years who was a member of a party other than the Democratic or Republican Parties, says Lou Dobbs is his choice for president in 2012. See this story. Barkley wishes Dobbs would accept the nomination of the Minnesota Independence Party. The only other time the Minnesota Independence Party ever had a presidential nominee was in 1996, when it ran Ross Perot. At the time, the party was the Minnesota branch of the Reform Party.
Although James Buckley was elected to the U.S. Senate in 1970 from New York as the nominee of the Conservative Party, Buckley was a registered Republican. Barkley was appointed to the U.S. Senate in October 2002 by Minnesota’s Governor at the time, Jesse Ventura, to fill the vacancy when Senator Paul Wellstone was killed. So although Barkley only served for a few months, he is the only minor party U.S. Senator since 1946, when Robert La Follette Jr. left the Wisconsin Progressive Party and became a Republican.
In Connecticut in 2006, Joe Lieberman was elected to the Senate as the nominee of the Connecticut for Lieberman Party, but, as in the case of James Buckley, Lieberman was never a member of the minor party that nominated him.