Nate Silver gives odds on them. He thinks Palin has a 3.2 percent chance of winning the GOP nomination:
There have been some “extreme” nominees before, like George McGovern and Barry Goldwater; that precedent is why I think that Ms. Bachmann is a plausible candidate. But no candidate has been nominated with unfavorable numbers as high as Ms. Palin’s. If someone like Ms. Bachmann is on the verge of winning the nomination, I expect you’ll see some efforts to prevent that — but these would be constrained at some point by fears about inflicting collateral damage upon the party (like harming turnout among base voters who will be critical to Republican efforts to win control of Congress). Ms. Palin, however, may be regarded as such an unmitigated disaster that you could see a floor fight at the convention, or threats by either Ms. Palin or a moderate candidate to run as an independent.
The Dish 