"I'm a Democrat, starting ... now!"Photo: Getty Images

Pennsylvania senator Arlen Specter, one of the few true moderate Republicans in the Senate, has announced that he will switch to the Democratic Party and run for reelection as a Democrat in 2010. This is a huge deal, not only because Specter has been a GOP member since the Paleolithic era, but because, assuming that Al Franken gets seated at some point in our lifetime, it will give the Democrats an unstoppable 60-seat supermajority, allowing them free reign to legislate at will without fear of a filibuster. We imagine frightened Southerners are already streaming out of their cities, pushing oxcarts with all their valuables as they flee to Mexico. In reality, though, it won't always be easy for the Democrats to keep the caucus completely cohesive. Specter noted in his statement that the Republican big tent has been getting pretty tiny over the years, and indeed, he would have faced a tough primary challenge from the more conservative Pat Toomey had he remained a Republican. But he didn't! Amazing.

Arlen Specter To Switch Parties [Fix/WP]