First, don't call yourself a comeback kid until you've actually won. And if you want to call yourself a comeback kid, don't go raising expectations before the results are announced.
Second, and more importantly, Mitt Romney is full of baloney on this. He "started out" way, way ahead in the polls. There was nothing down about it.
Before Santorum's February 7 mini-Tuesday sweep of Colorado, Minnesota, and Missouri, Mitt Romney's average lead in all Michigan polls had been 15 points. His lead was double digits in 9 of 12 of those polls. And Rick Santorum was such a non-factor, he didn't even get included in 5 of them. In the 7 polls that included Santorum, his average support was 7 percent. He didn't break double digits until the end of January.
Meanwhile, Romney's average in those same polls was 34 percent. So before mini-Tuesday, Mitt Romney led Rick Santorum by an average of 27 points. In one poll, Romney led by 38!
Even as late as early February, Mitt Romney had a 16 point double-digit lead. So assuming he pulls off a narrow victory tomorrow, it's hardly going to be a comeback. Rather, it will be a case of hanging on for dear life.