Starting at 3:05, Fund entertains this idea. No, Obama can't be primaried out, not really, because if you win, you lose, because no way do the 1/3rd of the blacks that make up the Democratic primary voting community welcome that. (In this scenario, Obama would be such a sure loser (only way it could happen in the first place) that many blacks would support the switch, but too many more would view it as the Democrats betraying the first black president, rather than sticking by him.)
The only way it happens if it's voluntary; Obama declines to seek reelection.
Maybe after it was strongly suggested he do so.
Kind of silly, but not really so silly: We are probably in a recession now, and the scary thing is, a recession might be the best case scenario.
Is this all Obama's fault? No. Europe is coming apart at the seams; Obama didn't do that. But he's been pushing us towards a European model. He just wouldn't be viable after that. Especially because it's pretty clear he's married to his One Big Idea (European social-democratic welfare statism) and this Rara Avis will not reinvent himself under any circumstances.
This is now a nontrivial possibility. Tiny chance. But we do sort of have to rouse ourselves into preparing for the possibility that as much fun as we're having at Obama's expense lately -- he may not actually be our opponent in 2012.