The Democrats, if they're smart (and some of them are) won't trust him anymore than we could. Specter has shown himself to be the quintessential TRAITOR....and NO ONE trusts traitors.
Remember the scene in the movie PATRIOT, when a Colonial tried to switch sides and help the British? What did Col Tavington say to him?
He asked him, Give me a reason why we should trust you...after you, you're trying right now to betray the side you came from.
Right now, the Democratic Party is in the unenviable position that a woman is in who just married a man who left his wife for her.
How can she be sure he won't turn around and leave her for someone else, just as he did to his wife?