I think Santorum's past is what will be holding him back. He has always had controversial stances on vital issues. The fact that he has a definition for his last name that isnt exactly flattering doesnt help.
Even if he takes Michigan, he'll have to use it to start a major boost to his campaign. His, like other GOP campaigns, is just too blah....its all about "Look at me waste millions of dollars on TV ads attacking everybody else"...in order to distract us from the fact that nobody knows what the fuck to do with the United States right now.