[I sent this from my iPhone, so please excuse any excessive brevity or
First, from a political perspective, instead of facing serious pressure from the Right (because of Toomey's primary challenge), he will now face serious pressure to move to the left on various issues. That's because he's now going to have to run in a Democratic primary, and though the party will do what it can to clear the field for him, he'll still likely face some competition. And whoever he faces in the primary will play up his or her own Democratic bona fides while attacking Specter's lack thereof. So Specter will have to do things to prove that he is a legitimate Democrat. And if he proves to be a major obstacle to Obama's agenda, he'll suffer for it; the honeymoon will be over very quickly.