As Lance Armstrong showed time and again, the best luck goes to the rider who is on best form and is best prepared. While bad luck can hit anyone, it's no coincidence that Basso has remained upright in this Tour.
Contador has looked a little ragged, it's true, but it's still too early to say definitively, or with any assurance at all, really, that he is not on winning form (since, for him, he can be at less than 100% and still win). So, for now, anyway, I'm sticking with him as my pick to win.
That leaves the second step for Basso. If Contador fails or withdraws, Basso will win the Tour. He is tranquillo.