Rick Santorum has slipped ahead of the Mitt Romney in the polls, marking an ignominious milestone in the Republican nomination: Since last summer, when Romney was at the top of the early polls, the lead has switched nine times. In order, it's gone to Rick Perry, Romney, Herman Cain, Romney, Gingrich, Romney, Gingrich, Romney, and Santorum, who now leads the Real Clear Politics' aggregated trend with 30.2 percent to Romney's 28.6 percent. Notice a pattern?
Santorum has also but he has overtaken Romney in recent polls in Michigan. On the strength of recent polls by American Research Group and PPP--two polling organizations which use questionable methodologies--the New York Time's Nate Silver has Santorum 75 percent likely to carry the state where Romney was born, his father served as governor, and he carried easily in 2008.
We are a little more cautious with Santorum; The markets suggest he is 55.7 percent likely to carry Michigan to Romney's 44.7 percent. These numbers have certainly moved in Santorum's favor over the last few days, but not nearly as much as in those models that rely completely on polling.....snip~