Of the three, I think Hamilton has the best chance at the championship. The McLaren is a very good car, and should suit at least four of the upcoming circuits. Hamilton’s biggest challenge is that he is going to need other results to go his way to stay in the title fight.
Raikkonen, I think, does not have much of a chance. He is probably going to need at least two wins before the end of the season if he wants to be champion, and he is probably going to need them sooner, rather than later. And for that to happen, Lotus really need to work on their race management.
As for Webber, he is such a rank outsider that although he is technically in with a shot, he will only be champion if Vettel suffers a string of problems with his car. Any time Red Bull is on or near the top of the heap, they will back Vettel because Vettel is much closer to Alonso than Webber is.