On Thursday, I warned you to be cautious about assuming that Mitt Romney had retaken the lead from Rick Santorum in Michigan until we saw some concrete evidence for it. Today, it looks like we have some.
A new Rasmussen Reports poll of Michigan gives Mr. Romney a six-point lead there, 40 percent to 34 percent. The poll, conducted after Wednesday night’s debate, represents a reversal from Rasmussen’s previous survey of the state, which had Mr. Santorum up by four points instead.
Mr. Romney also holds the lead in a second poll, from Mitchell Research and Rosetta Stone, which like the Rasmussen survey was conducted on Thursday after the debate. There is less in the way of momentum for Mr. Romney in this survey — he held a two-point lead in a poll conducted by the same firm earlier this week and has a three-point lead now — but it gives him an advantage nevertheless.
The FiveThirtyEight forecast model now projects a win for Mr. Romney by about four points in Michigan, roughly bisecting the Rasmussen Reports and Mitchell Research polls. Although that is inherently a fairly small margin, it is more meaningful given that there are just four full days of campaigning until Michigan votes; the model makes Mr. Romney about a 2:1 favorite in the state.

Mr. Santorum may now need to find a way to turn the news cycle back toward his advantage in some way. His “super PAC” has narrowed Mr. Romney’s advertising advantage in Michigan, so this latest shift appears to have been driven mostly by his middling performance in the debate, and perhaps also by his problems in rebutting controversies about his past statements on social issues.
Failing that, Mr. Santorum will simply need to outperform his polls on election day — something that he has succeeded in doing in several prior states. He could get a modest boost from Democrats — a group with which he held a clear advantage in the Mitchell Research poll — some of whom may be voting in the Republican primary for tactical reasons in an effort to prevent Mr. Romney from gaining too much momentum in the Republican nomination race.
For the time being, however, it looks like betting markets, which had always been somewhat incredulous about Mr. Santorum’s chances in Michigan after he surged in the polls there, may get some vindication on Tuesday. And so may Mr. Romney.