Obama removing Petraeus as a potential rival?

I can't help but wonder if a major part of Obama's strategy in getting Gen. Petraeus to take over from Gen. McChrystal is to make sure that Petraeus doesn't run against him in 2012. Petraeus has said he isn't interested in running for President, but a lot of people, including myself, have thought that he would be a great candidate. If he's over there in Afghanistan though, 1) he can't organize a presidential run and 2) the Afghan situation is such a mess that even Petraeus might not be able to fix it so that being in charge there will burnish his reputation.