Two other factors were in play, factors that led to sharp Democratic gains in these same areas in the 1970s. One was honesty. The outstate Midwest recoiled against Richard Nixon’s Republicans in the Watergate years, and this year, these voters had a similar reaction to Clinton’s e-mail lawbreaking and lies. That helped Trump, though it probably would have helped any other Republican nominee.

The other factor was dovishness. The Upper Midwest has long been the most isolationist part of the country. In the 1970s, voters there reacted against Republicans’ support of the Vietnam War. This year, they seem to have moved toward Trump, who opposed military interventions supported by other Republicans. It seems unlikely another Republican nominee could have duplicated this appeal.

So I find myself leaning reluctantly toward the conclusion that no other Republican could have won, at least the way Trump did. Yes, others would have run better with white college graduates, whom Trump carried by only a 49-45 percent margin, and would have run much better among groups with high levels of social connectedness, such as Mormons in Utah and Dutch-Americans in metro Grand Rapids, Michigan.

But Trump saw, or stumbled into taking advantage of, an opening spotted by only a few political analysts — blogger Steve Sailer way back in 2001, RealClearPolitics’ Sean Trende in a 2013 article series and FiveThirtyEight’s Harry Enten in analyzing Republican Joni Ernst’s big Senate win in Iowa in 2014. I made similar observations but didn’t nail it the way they did.