"My party has not defined who I am," said Republican apostate Arlen Specter, ending weeks of speculation on April 28 by announcing his decision to join the Democratic Party. No kidding. Upsetting party politics is old hat for the fifth-term Senator from Pennsylvania: back in 1965, as a candidate for Philadelphia district attorney, Specter shed his Democratic Party affiliation to run as a Republican. That move may have offended a few local pols, but the potential consequences of his more recent shift are more significant: it puts the Democrats one Al Franken victory away from a filibuster-proof majority.
The Crist Switch: Top 10 Political Defections
Florida Governor Charlie Crist announced April 29 that he will leave the Republican Primary and run for the U.S. Senate as an independent. He is not the first to change sides. Over the years, scores of politicians have danced from one side of the aisle to the other. TIME rounds up the top 10 political defections in U.S. history