As I noted before the Florida primary, early voting is something to keep in mind before we get all giddy about Romney going down in flames. If I’m reading the statute right, Michigan voters could begin requesting absentee ballots 75 days before February 28th. Early voting in Ohio began the same day as the Florida primary.
Romney won early voting in Florida, beating Gingrich to the punch chasing absentee ballots. So far, I have not seen any early voting numbers for these states as with Florida, but I would suspect Romney is following the same strategy as in Florida and chasing those absentee voters, as well as attempting to win the early vote.
It also remains to be seen if Santorum can withstand the onslaught of ads from Romney and his allies, especially in elections across multiple states on the same day, any better than Newt did in Florida.