The Democratic coalition has become more urban and cosmopolitan in recent decades (consider the contrast between Bill Clinton’s and Barack Obama’s style and platform), causing Appalachia to move toward the Republicans. As Democrats embraced more environment-focused energy policies, voters in coal counties have come to view Republicans as a more reliable ally. In other words, some of the most economically downtrodden white areas of the country were moving away from Democrats before Trump—in some cases so much that he had limited upside there.

A similar pattern explains why education wasn’t as predictive in the South as in other regions. In Mississippi, Alabama, Georgia, Louisiana, Texas, and Arkansas, the predictive power of education was much lower than it was in many Midwestern and mid-Atlantic states. That’s partially because Republicans have been increasing their hold on white working-class voters in the South for decades. The South’s transition from a top-to-bottom Democratic stronghold to a supermajority Republican region is a complicated story that involves economics, culture, and race. It’s sufficient to say that voting in the South became racially polarized before Trump came on the scene—that is, Republicans often win supermajorities of white voters, Democrats win supermajorities of African-Americans, and that gives the GOP a substantial edge in almost all statewide and national elections across the region (apart from swing states Virginia, North Carolina, and Florida). In other words, non-college-educated whites in the South were already voting heavily for the GOP, so Trump could only gain so much with them. …