There's a simple answer to the question, I think. He's going to be the next governor of Iowa, assuming that there are no stunning surprises next week and Chet Culver, the Democrat, doesn't mount a miraculous election year comeback.
Indeed, even as the last previous Republican gubernatorial nominee ahead of the Iowa caucuses, Branstad and his team would have quite a bit of influence over the field operation that a candidate Sarah Palin would need to recruit to win there
If you're thinking about running for president, and I think Palin really is thinking about running for president, you don't get on the wrong side of the guy who will probably be governor during the caucuses by endorsing his opponent, no matter how conservative and Tea Partyish Bob Vander Plaats seems to be. By the way: Vander Plaats's biggest proponent: Mike Huckabee, whose campaign he co-chaired in '08.