It wouldn’t shock me if McCain picked Huckabee, who I think would be a really bad choice, but I think it’s more likely he’ll pick a governor with a firmer conservative reputation that’ll solder up the base, or if not that, somebody who’s popular and comes from a swing state. Huckabee doesn’t have much to offer relative to others.
McCain comes across as unstable. There’s no telling who he would pick as a running mate. Hell, he’ll probably ask John Al-Querry.