It's a solid enough win for McCain, and he should get a nice bump out of it going into Florida. From the exit polling it seems that McCain's perceived electability played a major role and watching the speeches, it's not hard to see why Republicans might find McCain the most compelling of the lot. Here's the best bit from his victory speech:
As pleased as we are that we have a reason to celebrate tonight, I know that I must keep foremost in my mind that I am not running for President to be somebody, but to do something. I am running to keep America safe, prosperous and proud. I am running to restore the trust of the American people in their government. I am running so that our children and their children will have even greater opportunities than the ones we were blessed with. I am running so that every person in this country, now and in generations to come, will know the same, sublime honor that has been the treasure of my life: to be proud to be an American.
After that, the crowd erupted into chants of "USA, USA." The last time we saw that was when McCain won New Hampshire, and before that at Obama's victory speech in Iowa. In each instance, it was evidence of an invigorated and optimistic campaign, though such public displays of patriotism almost certainly play better on the right (see Dean's post below, " Obama Not a Real Democrat?"). More commentary on what it all means from Mark Steyn at the Corner and Abe Greenwald at Contentions. And a few other explanations for why McCain won from Marc Ambinder.