"In any case, open-seat presidential elections like 2008 just are different in character from incumbent reelects, and I think that's the most important thing about this election - is that once there's an incumbent running for reelection, most of the debate is about, "Has he [Barack Obama] done a good job?" Most of the judgment is, "Do you want to keep him or do you want to replace him?" Now, the opponent has to also be acceptable and has to make his own case."