Wiggins could do it, and of course Cancellara. But the overall win is not as interesting to me as is the order of finishing for the GC contenders, and the time gaps among them.
I think Armstrong will definitely go all out and try to win this like in the good old days, for himself as much as for anyone else. If he wins, or even just beats Contador, he will demand to be the team leader (barring being dropped in the mountains). This prologue appears to be a relatively good measure of overall condition.
However, I only give Armstrong a 40% chance of succeeding. I am impressed with his apparent improvements since the Giro, training in the CO mountains (except for the one day in Nevada City), dropping the weight, TT specific training, etc., but he is 37 and Contador was smokin' in Spain this morning.
Ignoring Armstrong, Contador does not have quite as much to prove. He is the defacto team leader, and theoretically all he needs to do is not lose more than a few seconds to the other GC contenders, so he might hold off a bit, relatively. But, he knows his leadership might be in jeopardy if Lance beats him, especially if by a significant margin, so he might decide to not hold back anything either.
Levi knows he needs to save himself, and with AC and LA on his team, and given his faltering (relatively) form, he's probably not going to go for it, and probably couldn't win at this point anyway.
Cadel looks to be in the form of his life and might pull this one off.
1. Armstrong
2. Evans
3. Wiggins
4. Cancellara
5. AC