In my book “Hard Heads, Soft Hearts” (1987), I bemoaned that it was difficult to be both a Democrat and an economist. Democrats, I wrote, often advocated economic policies that were well-intentioned but softheaded. Yes, ends matter, but so do means.

Later, it became easy to be a Democrat and an economist because the Republican Party went nuts with supply-side economics, the notion that “Reagan proved that deficits don’t matter,” and the wacky idea that “trade wars are good, and easy to win.” The GOP continues to fail basic...