For my money, Charles Krauthammer's the smartest and most persuasive neoconservative out there. Yet even he's skeptical about Petraeus' Afghanistan mission for reasons that Obama is probably powerless to change.
The problem, as Krauthammer sees it, is that Afghans won't start relying on us to protect them from the Taliban until they're persuaded that we're going to stay there for the long haul. Assume that he's right. Does anyone really believe that Obama could persuade Afghan elites of our steadfastness by reciting the words of determination we used to hear from George Bush about Iraq? That only makes sense on the bizarre assumption that Afghans are more inclined to take American politicians at their word than all but the most innocent Americans.
What an irony it would be if Obama found himself upholding a neocon position that even Krauthammer won't endorse.