The soon-to-be retirees. Photo: US House of Representatives and US Senate

Pundits underestimated Donald Trump for many reasons in 2016. But one was that the mogul’s support was weakest among the peculiar subspecies of Republican we in the “Fake News” media are most likely to know: urban- or suburban-dwelling, college-educated fiscal conservatives with relatively moderate views on culture-war issues.

That fact likely informed this infamously self-assured pronouncement Chuck Schumer made in summer 2016: “For every blue-collar Democrat we lose in western Pennsylvania, we will pick up two moderate Republicans in the suburbs in Philadelphia, and you can repeat that in Ohio and Illinois and Wisconsin.”

Schumer’s math was, of course, less than accurate. Trump really did drive a significant number of suburban Republicans out of red America, but such voters were largely concentrated in safe blue states like California and New York or in “not quite competitive” Sunbelt ones like Texas and Georgia. Thus Trump’s gains with the (numerically much larger) white non-college population proved far more consequential in electoral terms. Moderate suburban Republicans may have an outsize voice in elite discourse, but, as of three years ago, they had precious little clout in the Electoral College.

Yet the president’s toxicity with “New York Times op-ed-page Republicans” has nevertheless created two major problems for his party: (1) When GOP-controlled state governments drew their gerrymandered House maps in 2018, they deliberately inflated the influence of suburban areas on the presumption that such places were Republican strongholds, and (2) the type of Republican who serves in Congress is disproportionately likely to be a highly educated, urban- or inner-suburban-dwelling fiscal conservative with relatively moderate views on immigration (for a Republican, anyway).

These two issues helped doom the GOP’s House majority in 2018 — both by increasing the number of battlegrounds where Democrats could compete and by driving Trump-averse GOP incumbents into retirement. These same factors appear poised to ensure that Democrats retain control of the chamber in 2020.

A Washington Post story on the GOP’s recent spate of retirements spotlights the importance of problem No. 2:

Republican Rep. Paul Mitchell’s surprise retirement began with a President Trump tweet.

Moments after Trump’s July 14 missive telling four U.S. congresswomen of color to “go back” to their countries of origin, the congressman from Michigan phoned a fellow House GOP leader and asked him to get Trump to stop. “It’s the wrong thing for a leader to say,” he told the leader, whom he declined to name. “It’s politically damaging to the party, to the country …

Mitchell is among a growing list of House Republicans — 18 to date — who have announced plans to resign, retire, or run for another office, part of a snowballing exodus that many Republicans fear is imperiling their chances of regaining control of the House in the 2020 elections …The retirement numbers are particularly staggering. All told, 41 House Republicans have left national politics or announced they won’t seek reelection in the nearly three years since Trump took office. That dwarfs the 25 Democrats who retired in the first four years of former president Barack Obama’s tenure — and Republicans privately predict this is only the beginning.

Some of these retirements have been inspired by darkening reelection prospects, but others appear rooted in personal aversion to Trumpism. To be sure, college-educated GOP lawmakers are likely to have stronger partisan attachments and ideological commitments than their demographically similar co-partisans. But to cost his party the advantages of incumbency in a bunch of House districts, Trump doesn’t need to turn Republican Congress members like Paul Mitchell into Democrats. He just needs to turn them into lobbyists, consultants, or commentators. Which is to say: To devastate their party, moderate GOP lawmakers don’t need to find Trump so alienating that they’d rather sacrifice their policy preferences than vote for his reelection; they just need to find him so alienating that they’d rather cash out on K Street than fight to keep a job in which they’re forced to answer for his tweets.