Mitt Romney scored two impressive wins tonight. He won Arizona by a clear margin of more than 20 points, so much so that he would have won even if none of the voters in the most pro-Romney demographic (the one-ninth of the electorate who were Mormons) had shown up at the polls.

In Michigan, exit polling showed 52 percent of primary voters were tea-party supporters. Romney actually carried those voters narrowly. In Arizona, where almost two-thirds of primary voters identified with the Tea Party, Romney carried that group by seven points. If the Tea Party can be considered the fiscal-conservative heart of the the Republican party, Romney fared better with that group tonight than anyone else.

Santorum did well with evangelical and pro-life voters, but the clear implication of tonight’s results is that he has trouble building a truly across-the-board coalition. Romney came closer to that tonight, and if he replicates his Michigan showing in Ohio on Super Tuesday, he will be much closer to wrapping up the nomination.