One of the scariest and most interesting people in American political culture. Although he's probably best-known as the man for whom three thousand elderly Jews accidentally voted for, he is much more than that.
As an advisor to Richard Nixon, he was a prime player in the Southern Strategy that brought him to two consecutive victories, one of them a 49-state sweep. He also coined the term Silent Majority(ironic, given that they then sided with the loudest and least justified screamers of all).
In 1992 and 1996 he attempted to run for President in the Republican Party primary, losing both times. He left the GOP due to its increasing embrace of neoconservatism, and in 2000 he won a bitterly-contested match with John Hagelin for the nomination of the Reform Party previously run by Ross Perot. He returned to the Republicans in 2002, and endorsed George W. Bush in his re-election attempt. At this point he now works with MSNBC and appears frequently with liberal commentator Rachel Maddow, who appear to be good friends despite Maddow being an open lesbian and Buchanan being homophobic.
What really intrigues me about Buchanan, though, is the way that he can say things that are mostly reasonable much of the time on MSNBC but then he can go on The Colbert Report and make Stephen Colbert look like the straight man by coming within inches of defending Adolf Hitler. A Slate article about snubs quotes Buchanan's Crossfire colleague Michael Kinsley(most notable for the Kinsley gaffe) that a lot of people refuse to come on TV with him not because of his views but because he's just that good at debating.