Keep this theme in mind for the next year and change: most Republicans running or stoking speculation are actually campaigning for the Veep slot and/or Cabinet appointments in the next GOP administration.
Thanks to the lack of a clear front-runner for the GOP nomination (Romney, Huckabee and Palin seem to be jockeying for the lead at this point, with none having a clear advantage over the others), the media is being treated to a glut of candidacies that can only be described as whimsical. Herman Cain, Rick Santorum, Kook-Kook-a-Choo, Newt Gingrich, etc. And now the speculation has begun about non-candidacies from Marco Rubio and Chris Christie, the n00bz of the GOP salon scene.
But I don't think these minor figures are, for the most part, seriously looking to get elected President. Rather, I think they're preening in advance of someone else's candidacy.
Romney's considered too centrist for far-right tastes. He needs to be able to pick someone to head off a convention floor fight. Herman Cain--black, rich, wildly anti-health reform, and as likely as Palin to say crazy things--is a good fit for his ticket. Rick Santorum would work as well, as a bone for the anti-gay crowd.
Huckabee is positioning himself as the Values Voter's wet dream (do "Values Voters" get those?), so he needs someone who can boost him with other constituencies in order to put more states in play. Rubio is a great fit for that--young, Hispanic, only mildly corrupt, and from a high-value swing state.
Palin needs to have someone who at least appears to know what the hell he's doing. Newt, Huntsman or Bolton would fit well with that purpose (though I doubt that even ambition would get Huntsman to campaign with her). But, let's be honest, there isn't enough support among GOP leaders for her to be nominated, and I doubt she's planning to run for exactly that reason (at least, not on the Republican line, but the Constitution Party would probably love to run her, and it's not like the Palins have an aversion to minor parties).