I see Mitch as a strong VP candidate. Guys that look good on paper and can help in Swing states. Other strong VP contenders are Petreaus, Thune, Hutchinson. But a smart VP pick will help win Ohio and even Santorum might be able to do that.
But Mitch doesn't have a large personality. He's the Republican version of Evan Bayh, boring mid-westerner with a good political resume but no one is excited to vote for him outside of Indiana. Mitch could win Iowa and grind out a national campaign against Obama, but at this point he's not Bill Clinton and doesn't have GWBush's family name recognition to win voters. He's not even a War Hero like McCain or Kerry.
Sadly, Romney could win the nomination by Default because everyone is 2nd tier. But Romney's barely above 2nd tier himself, with a very small base somewhere in michigan, utah, and NH.
Pretty much this. It's a better idea for Daniels to be a VP candidate and run later on. Nevertheless he still has a high chance though.