At the moment if I were to gamble, I'd go with Rubio, but the risk of him becoming a Republican Obama does seem considerable.
Kasich is still sounding like he could be not only a good president but also a much-needed reconciliator - but it's immaterial as long as he has no chance of winning the primary. Put him in the general and I'd like his odds.
Still not taking either Trump or Carson seriously - both would be atrocious choices. Fiorina's moment seems to have passed as quickly as it came. Cruz might have a shot down the line at the primary, but no shot in a general election. Bush and Christie have the opposite problem, like Kasich.