Arlen. Welcome my friend, welcome.

When combined with the eventual and inevitable outcome of the death march otherwise known as the Norm Coleman campaign in MN Specter's switch will give the Dems an on-paper filibuster proof majority, however in real terms it changes very little as Specter has long been a reliable swing vote.   The real gravy here is how this supports the narrative that the GOP is down to its 

bat shit crazy core and getting crazier by the day.   On the heels of national polls showing that party identification is at its lowest levels in more than a generation the news that a senior senator like Specter fears he would lose his state party primary but is confident that he can win a general with a different party isn't helping get any poles up  in that big tent.   The GOP will get a lot nuttier before things get any better.