Um, and why is Specter changing parties good news?

I think the whole thing doesn't matter that that much; it's not like cloture votes during this congress have come down exactly on party lines, and that Specter will now necessarily vote for cloture whereas previously he would have voted against. Hardly.

Had Specter stayed with the GOP, the CW, and I think it was probably correct, was that he would have lost the primary to the very conservative Toomey. And then it's not particularly likely that Toomey would have beaten the Democratic candidate, whoever that would have been. So we most likely would have ended up with a 'real' Democrat in the seat after the 2010 election.

As it is now, any Democrats challenging Specter in the primary will likely have a tough battle.