It's hard to say, I guess it depends on what he wants to do. VP would have been a dead end whether Kerry won or lost, in my opinion. Republicans would have disowned him and Democrats wouldn't accept him. If he really wants to and thinks he can make a difference, I think he could take a cabinet position without nearly as much flak from both sides as he would have caught accepting the VP. Guess we'll wait and see. Hopefully we won't have to find out.
