Mitt Romney and Rick Santorum slugged it out tonight in Arizona, but the importance was all about Michigan. Santorum, as the frontrunner in the polls, was on the defensive for most of the night. Romney, as the actual frontrunner, was playing it safe. The strategy paid off for Romney. During the course of the debate, his likelihood of carrying Michigan rose from 66.2 percent, 15 minutes before the debate, to 73.6 percent, at the close of the debate. And, in correlation, Romney’s likelihood of gaining the GOP nomination is up over 3 points on the day to 75.7 percent.