Tyler Cowen thinks that Obama's proclamation that "I'm no VP" is a bad political move, because it frames the debate around the question of whether he could be VP. Framing effects are real, but I think their effect is overstated in political races. You can shift the focus of the debate to some extent, but voters are not actually completely stupid. The Democratic attempt to reframe tax hikes as "user fees" or "investments" or what have you died on the vine because they came up against a hard reality: most people don't want to let go of any more of their paychecks. This remains true whether they're paying taxes, keeping up their membership in the vast green country club that is America, or getting in on the national health care IPO.
Hillary was trying to tell voters that they might be able to have their cake and eat it too, a not unattractive proposition. I see Obama as doing the equivalent of throwing the steering wheel out the window. Now we see whose voters run off the road first.