Last spring, Ramesh Ponnuru wrote a prescient article for National Review on the intra-Republican class divide:

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. In recent elections, upper-middle-class voters have left the Republican party in part because they regard it as dominated by yahoos and know-nothings. But other voters, particularly in the party’s base, resent what they see as a tendency to overestimate the importance of degrees from prestigious colleges. In the Delaware Senate race, populist candidate Christine O’Donnell started an ad by saying, “I didn’t go to Yale.” (Romney has two degrees from Harvard, Palin one from the University of Idaho.)
There would even be religious overtones to the conflict. Some voters find his Mormonism, and some voters find her evangelicalism, problematic. (And some voters would probably prefer to have a candidate without a strong religion at all, although few of them vote in Republican primaries.) Even if both candidates tried to keep the race from becoming a religious conflict, hotheaded supporters could draw them into one.
The 2008 presidential election was a festival of identity politics in both parties: upper-middle-class white women voted for Hillary Clinton, Mormons and rich people for Romney, evangelicals for Mike Huckabee, young and inexperienced voters for Barack Obama. If Romney and Palin are the top Republican contenders, the next presidential race could become even more tribal.
Not to mention ugly. 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. …
If, as seems more likely, Romney won the showdown, he would have alienated a large chunk of the party’s conservative base. He would therefore have to solidify core Republicans before, and sometimes at the expense of, trying to court independent voters. And he would have another problem as well. In his 2008 run, he showed almost no ability to win over middle-class voters. If he beat Palin, he would almost certainly have won with an affluent coalition inside the party and while being mocked as a blueblood. He would then have to turn around and win both downscale conservatives and middle-of-the-roaders.

To be sure, Palin isn’t running. But Rick Perry and Newt Gingrich have been attacking Romney as a heartless capitalist. Perry in particular seems eager to play the Palin role. Because the Palin role is divided among several candidates, including Rick Santorum, and because none of the candidates match Palin in terms of charisma or visceral appeal, the situation might not be quite as grim as Ramesh envisioned a Palin vs. Romney clash.

Yet it is true that Romney is, so far at least, winning on the strength of relatively affluent voters, as suggested by the New Hampshire exit polls. As you climb the income ladder, Romney gained strength, winning a 51% majority among $200K+ households and 45% among $100-200K households.

This could suggest that a Romney coalition would include a somewhat higher share of the upper-middle-class electorate than the McCain coalition in a general election. One can imagine Romney faring relatively well among “Post-Moderns.” The question, however, is whether these gains will be accompanied by erosion among “Disaffecteds,” per Ramesh’s conjecture.