Perhaps most significant, Kitschelt and Rehm found that the common assumption that the contemporary Republican Party has become crucially dependent on the white working class — defined as whites without college degrees — is overly simplistic.

Instead, Kitschelt and Rehm find that the surge of whites into the Republican Party has been led by whites with relatively high incomes — in the top two quintiles of the income distribution — but without college degrees, a constituency that is now decisively committed to the Republican Party…

High-income whites without college degrees were swing voters sixty years ago, pursued by both parties; now, they are rock-ribbed Republicans. Their share of the white electorate has fallen, however, from 42.1 to 22.0 percent.

Two generations ago, there were almost no low-income whites with college degrees, a group that made up 1.5 percent of white voters in 1952. These voters were a swing bloc without firm commitment to either party. By 2016, this constituency had grown to form 14.3 percent of all voters. They have, in turn, become the most loyal white Democratic constituency.