It might be that Huck is fighting the last war. He’s up with that ad in Michigan attacking Romney for looking like a lay-off artist. This might have made sense when Romney was the guy who everyone needed to get out of the way to have any chance at winning the nomination. Now, Romney is no longer that guy–McCain is.
Plus, McCain is the graver threat to Huckabee in his must-win state (sorry VDH!) of SC. If McCain wins Michigan with the help of Huckabee tearing down Romney, he’s going to get a bump in SC where he is already surging, and Huck is in big trouble. Huck might be thinking he can get a bounce out of a second in Michigan, but it’s usually the case that the first-place bounce is much bigger than the second-place. So Huck can finish second, but if McCain finishes first, he’s 2 for his last 2, and looking strong in SC. And if he wins there too, he might be on his way to the nomination.
Now, if I were Huck, I might calculate that my odds of actually taking down McCain are slimmer than my odds of playing very nice with him, continuing to act as his de facto stalking horse, and getting picked by him as his running-mate. It will be interesting to see if Huckabee is more aggressive against McCain tonight, or if he’s still teaming up with him against Romney.