Ramesh Ponnuru envisions one:

[It would] be a straight-up power struggle between the tea parties and the Republican establishment... Class is another increasingly uncomfortable fault line in the party (as Reihan Salam and I recently described in these pages). Romney’s supporters tend to be college-educated, while Palin draws her support from people who didn’t get college diplomas... There would even be religious overtones to the conflict. Some voters find his Mormonism, and some voters find her evangelicalism, problematic.

He also notes how personality would be a huge factor:

Palin is not the type of politician who ignores unfair attacks. Instead she invites her fans to share her grievances. Any presidential candidate, and especially a polarizing one, will be on the receiving end of a lot of cheap shots. (Also on the other end.) Count on her or her supporters to turn every dismissive remark or ambiguous statement into a sexist or elitist putdown of millions of voters and to make sure that everyone hears about every actual offense against her.

The main difference between Palin and Romney is that Palin is a star who commands a cult; Romney is a cipher who hires a lot of staff.

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