Republicans have reached their 1984. I don’t mean this in the Orwellian sense, though Republicans have more than their share of Orwellian impulses. Rather, I mean that the kind of divisions that have characterized Democratic presidential primaries since the 1984 contest between Walter Mondale and Gary Hart have now popped up in GOP primaries as well: This year, Republicans are dividing along lines of class.

According to data compiled by the Wall Street Journal, in all the states that have voted thus far, Mitt Romney has won 46 percent of the counties with incomes higher than the statewide median, and just 15 percent of those with incomes beneath the statewide median. Rick Santorum, by contrast, has won 39 percent of the counties with higher income, and 46 percent of those with lower income....

These numbers look familiar to anyone who has tracked Democratic presidential primary voting for the past three decades. Beginning with the Hart-Mondale donnybrook, Democratic voters have often clustered by class. In that year, Mondale, the presumptive favorite, was given a tough race by Hart, whose supporters were disproportionately upscale, younger professionals more concerned with environmentalism and cultural issues than with the bread-and-butter staples of New Deal politics. Mondale’s key backers were more downscale voters, disproportionately union members and African Americans, and his platform emphasized more traditional liberal priorities....