Democrats picked up a Senate seat in Arizona this week because Donald Trump is a raging egomaniac.

That’s not to take anything away from Kyrsten Sinema, the victor, a shrewd and frequently underestimated politician who ran a well-executed campaign against a formidable opponent. Arizona is a fairly conservative state. Trump won there, after all, Gov. Doug Ducey cruised to reelection, and Arizona hasn’t sent a Democratic senator to Washington in more than 30 years. Even in a rough national environment for the GOP, an incumbent should have been able to win here.

And Republicans had an incumbent: Jeff Flake. But Trump drove him out of the party for no real reason. Flake complained from time to time about Trump’s personal style, but ultimately, he voted Trump’s way on every big bill. The issue was Trump’s ego, not policy or politics.

It’s just another reminder that while Trump’s initial triumph in the Republican presidential primary was impressive, almost everything since then has been a mix of good luck and bungling. As long as the institutional Republican Party is dedicated to propping up his administration, he’ll remain in office. But the GOP will continue to pay a price.

Flake was normal. Trump made it weird.

Flake, like all Republicans, was overwhelmingly supportive of Trump’s legislative initiatives and nominees. That’s largely because Trump adopted a fairly conventional conservative agenda, not because Flake was hypnotized into loving Trump. The point, however, is that whatever qualms Flake had about Trump, they were never serious enough for Flake to want to jeopardize anything important on the policy front over it.

Which is just to say that Flake was acting like a normal senator.

Trump was a bad fit for Arizona, a state with lots of Latinos and a large Mormon minority, which he carried with considerably less than 50 percent of the vote. Senators representing states where Barack Obama was unpopular weren’t shy about distancing themselves from him at times even while mostly voting with him. For Flake to do the same was basically unremarkable.

Except Trump didn’t see it that way. Instead, he got himself embroiled in feuds with Flake that turned GOP primary voters against him. That eventually persuaded Flake to stand aside for the good of the party, so a solid candidate like Martha McSally could win the nomination. Flake didn’t want to stand and fight only to lose to the likes of conservative primary challenger Kelli Ward and jeopardize the seat. Instead, McSally ran — and lost the race anyway. And it’s not the only loss that can be put on Trump’s shoulders.

The electoral Trump tax is large and real

Trump pulled a similar move on Tennessee Sen. Bob Corker, who, unlike Flake, didn’t represent a swing seat in the Senate. Since Tennessee is so conservative, in this case, Rep. Marsha Blackburn was able to win on Election Day. But driving Corker from the Senate attracted a strong Democratic challenger in the form of former Gov. Phil Bredesen, which forced the GOP to invest money in what should have been a gimme race.

That money might have been useful to McSally or to Nevada Sen. Dean Heller, who lost last week in a somewhat strange way.

Heller’s problem wasn’t criticism from Trump; it was, rather, that even though Hillary Clinton carried the state, Heller never allowed an inch of daylight between himself and the president. Trump’s revealed preference was for every Republican in Congress to run as a Trump clone, but running as a Trump clone in a state Trump lost led, rather predictably, to Heller losing.

Colorado Sen. Cory Gardner is up for reelection in 2020 and appears to be staring the same fate in the face. It’s not impossible for a Republican to win a Senate election in Colorado, by any means, but Trump is clearly not popular there, so common sense is that Gardner should distance himself from the White House on a topic or three. But Trump doesn’t tolerate dissent, so Gardner has spent the past two years sleepwalking down the same path as Heller.

Trump himself called out a large number of retirements among House incumbents as a factor in the House GOP’s midterm losses. Yet he doesn’t seem to understand (or care) that he was a major driver of those retirements. Lots of House members in seats where Trump was unpopular didn’t want to choose between the Flake path and the Heller path, so they chose to simply retire and lay low.

These are just a range of ways the GOP is paying a “Trump tax” by anchoring themselves to a political leader who declines to behave in a normal or appropriate manner. And Republican leaders should at least consider the reality that Trump’s steady low-40s approval rating represents a ceiling rather than a floor. The country is, after all, enjoying a doze of peace and prosperity the likes of which it hasn’t seen for nearly 20 years. If a Republican president isn’t popular under these circumstances, what’s it going to take?