AP broke the news a few minutes ago.
Discussions on Fox News are saying that this makes Romney a favorite for VP (helps with unifying the right and talk-radio folks, helps in Michigan and the west, helps with potenially drawing upon Romney's money).
Also speculation that Romney's delagate going to McCain get him close to the magic 1191 that will be when Huckabee drops out . . . so this could be the move that makes Huck get out of the race . . . ah, sweet justice.