Wisconsin, like my home state of Michigan, doesn’t have party registration. Any registered voter can walk into the polls and vote in either the Republican or Democratic primary. In 2008 there were serious contests in both parties in Wisconsin. In 2012 there’s a serious contest only in the Republican primary. According to the exit poll, 30% of Republican primary voters identified themselves as Independents and 11% as Democrats. Among self-identified Democrats, Rick Santorum beat Mitt Romney 37%-19%. That amounted to a Santorum popular vote majority of 2% of the total vote. You might want to keep that in mind in interpreting the statewide percentage. Among self-identifed Republicans, Romney won 51%-37%. That’s pretty conclusive about what Republicans want.

Look at a couple of other results. Rick Santorum, the champion of opposite-sex marriage, carried the 30% of primary voters who are unmarried by 37%-32%. I’m guessing (and am pretty sure about my guess) that the great bulk of crossover Democrats are unmarried. Santorum also carried (and Ron Paul ran second among) the small number who said Romney was too conservative; he carried, narrowly, those who say the economy is getting better (which includes all those Democratic crossovers); he carried those who disapprove of Governor Scott Walker. In other words, Romney consolidated the Republican vote in Wisconsin, and Santorum’s total was boosted by crossover Democrats who want the Republicans to nominate what they believe to be a candidate who would be easy to defeat.