By winning Arizona and Michigan, Mitt Romney did what he needed to do. Rick Santorum had an opportunity to win the popular vote in Michigan and even pull off an upset in winner-take-all Arizona. That opportunity slipped away. Santorum could still win most of the delegates out of Michigan, however, and he has revealed some serious Romney weaknesses. The primaries and caucuses have also tended to be independent of one another this year, with little momentum. A good night for Romney but we will have to see what it means going forward.