The latest polling shows Romney with a tenuous lead in Michigan. There has been no measurable momentum for either Romney or Santorum. Meanwhile, Santorum could win with Democratic votes. His campaign is robocalling Michigan Dems asking for their votes.

Last week David Plotz gave voice (@8:19) to an interest theory on the rise of Santorum. It goes something like this…

Romney’s whole campaign has been based on the economic case against Obama. His competitive edge was supposed to be his 25 years as a businessman and entrepreneur. The angry conservative and libertarian Tea Party was never all that enamored, but they would come around.

Now, with the nascent Obama recovery, that economic argument is much harder to make, especially by a guy whose been none-too-nimble on the campaign trail. So what’s an extremely angry anti-Obama conservative to do?

The Obama administration move on contraception gave that anger a place to go. Where six months ago the socialist Obama was bankrupting the nation and impoverishing our children by burying then in the national debt, now the case that resonates against Obama is that he’s an anti-religious zealot leading our kids into sexual promiscuity.

And there you have it, the Santorum surge.

Image credit: Andrew Sullivan’s Headline of the Day. Really.