As it is the US has hugely strengthened Iran by handing Iraq over to Shi’ites and an Obama administration might try to capitalise on that by making a US-Iranian deal the cornerstone of Middle East politics, thus reducing Syrian, Saudi and Egyptian leverage. Iran would obviously be greatly tempted by such a deal. But if Obama and Ahmadinejad really could reach a deal it would probably be very bad news for both Hizbullah and Hamas, who might get cut off from Iranian aid. If that happens, I can’t see much joy for Palestinian militancy.
Unfortunately, I don't think it makes sense. Iran wants to be the dominant player in the Middle East; it has essentially succeeded at this, through its support of Hamas and Hezbollah, and the American fiasco in Iraq. This being so, I don't see what the Americans have to offer Iran, politically, to make them give up the regional prestige that comes from backing anti-Israeli militias.