I had two flashes of insight last night. First, I suddenly realized that it's possible that no Republican is going to win enough delegates to win the nomination before the convention in early September. Second, Romney's going to win the nomination. {And, this flash is independent of the first flash - Romney may well win the nomination before the convention.}
I think Romney will win because he's younger and fitter than either McCain or Giuliani, less likely to burn out or - as they will - appear old and irritable. Also, he's more of an unknown than either of them, so he has a better hope of building momentum. And, he's much closer to the Republican core values than is Huckabee, who I think could win enough delegates to play a big role at the convention.
I think the Democrat race will be decided one way or the other by early February, but thanks to the wide open Republican race we'll get a great chance to learn about the arcane primary system. Congressional Quarterly has the best summary I've seen of how the primaries work on a state by state basis. Also, these January primaries are all against the rules, which means that each of these states' has had their delegate totals cut in half.