Just so I get it on the record, I think the chances are about 80% or higher that it will be either Portman or Ryan, with Portman the favorite. There is heavy lobbying for Ryan by some on the conservative side.  Since Romney's chances to win are not good without Ohio, I think in the end he goes with Portman.  Nate Silver ran his model 50,000 times, and says Portman does the most to lift Romney's chances of winning the election (by about 2%), though Rubio does the most to increase chances of winning one state (Florida). I think Romney thinks he can win Florida without Rubio. If he pick Rubio, then he is going for a Colorado/Nevada strategy instead of Ohio.