Chait isn't sure that the establishment can beat Palin:

I wish them well, being more than willing to trade away the higher chance that Obama would beat her in order to avert the risk that she could actually win. But I see two serious problems with the establishment's anti-Palin campaign. The first is a coordination problem. Palin has very intense support. There are many Republicans who would like to carry the anti-Palin banner. But if they all run, they'll split the non-Palin vote. What they really need is to have a primary-within-a-primary for non-Palin Republicans, with the losers pledging to support the winner. Perhaps they can find some non-electoral mechanism to do that. (Fund-raising contest? Rock-paper-scissors tournament?) In the absence of that, none of Mitt Romney, John Thune, Haley Barbour, or any others has an incentive to abandon the field to any other Palin alternative.

Second, and more seriously, the Republian establishment has lost legitimacy among Republican voters.