To follow up on what Jamelle says below, I think it would be an excellent idea for Barack Obama to start praising conservatives, precisely because it would alienate them from their fellows. There's little point in giving a shout-out to those who are actually working with him in good faith. When they inevitably get purged from the movement for winning the praise of a man that many conservatives believe is intentionally trying to destroy America, the right will merely get a bit more conservative, continuing a trend it's been on for some time.
But what if Obama sowed confusion and suspicion among his opponents by praising not the moderates but some of their most stalwart members? He could do it, furthermore, with the subtle insinuation that the target has been working with him all along. "I want to give a special mention to Jim DeMint, who has been really helpful -- oh wait, I've said too much." The results could be dramatic.
I'm kidding, of course (sort of). But it's true not just that politics is personal but that we define our political views in no small part by what, and whom, we're against. For instance, I think part of the reason Republicans turned climate denial into part of their political identity -- and the fact that such beliefs have grown substantially over the last few years -- is that if you agree that the planet is warming and we ought to do something about it, that means you're agreeing with Al Gore, and that's just intolerable to some people. (That's just part of the story, but it may well be a meaningful part.)
Particularly if he wins re-election, conservatives are going to define themselves for some time by how much they hate Barack Obama and despise everything he ever did. Why not use that to your advantage?
-- Paul Waldman