Washington — A friend just returned from some time with a group of wealthy conservative donors. “They were ambivalent about Donald Trump two years ago,” he said. “Now they are vociferously pro-Trump. There’s a psychological study to be done here.”

Those in and around Republican politics have seen this dynamic at work. In spite of past misgivings, most GOP partisans seem to have accepted the idea that Trump is their guy in the broader culture/political war. They have rallied to his defense in a way reminiscent of how Democrats rallied to Bill Clinton during his scandal and impeachment.

The problem, of course, is that Trump — unlike Bill Clinton — is incapable of effective outreach to less partisan voters. To the contrary, he has confirmed public suspicions about his unfitness and instability. There is no measurable sense in which Trump has grown into the office he holds. He remains defiantly nativist, instinctually divisive, habitually offensive. A significant portion of the voting public has gone from ambivalence about Trump to alarm, hostility and disdain.

So, in the 2018 midterm election, Trump tried to nationalize the election on issues that motivate his party — appealing to those voters who are excited by exclusion. And GOP partisans responded by turning out in large numbers. But it was not nearly enough to counteract greater public fears.

In other words, the politics of partisan mobilization only works if you don’t scare the rest of America to death. Republicans have come to the defense of a man who is incapable of widening his appeal. And this has opened up a reality gap between the GOP and the rest of our political culture. The rift between Republican perceptions of the president and the view of the broader public has grown into a chasm. This is now the main political context of the 2020 campaign.

Why have Republicans fallen in line with a politician who has sometimes targeted their own party and leaders for populist disdain? Why have conservatives come to the defense of a leader with decidedly unconservative views on trade and foreign policy? Why have religious conservatives embraced the living, breathing embodiment of defining deviancy down?

This phenomenon would benefit from a psychological study. Those who violate their own beliefs for political gain — elevating the ends of politics over the means of character — become mentally invested in their choice. Admitting that Trump is a chaotic and destructive force in Americans politics would require self-judgment. There is a reason that enablers enable — because a more objective self-assessment would bring guilt and pain.

At one level, the reality is not complex. Trump is a populist demagogue who gains permission for his brand of politics by giving favored groups certain ideological benefits — particularly a tax cut, regulatory relief and conservative judges. I happen to agree with some of those decisions. But they are part of a system or structure that was created to provide legitimacy for a general lowering of political and moral standards.

At the level of raw politics, this deal has worked. A president who panders to the religious right may end up being more reliable than a leader who is actually a religious conservative and thinks for himself or herself. Pandering is utterly predictable. Conscience makes distinctions.

But there is a downside to the deal. This particular demagogue requires not just consent but approval. And not just approval but obeisance. So religious conservatives end up blessing what Pete Buttigieg memorably called “the porn-star presidency.” Deficit hawks vote for massive increases in debt. Economic conservatives accommodate the instincts of an economically illiterate leader. Military hawks endorse a foreign policy that resembles Barack Obama’s, except with more praise of dictators and less backbone.

To ensure the political triumph of their views, these partisans must publicly dilute and discredit those views. Trump offers true believers an uncomfortable arrangement: What you would save you must first defile.

The historical judgment on that deal depends on how destructive Trump ends up being to our public order. Making the case for Trump requires his advocates to consistently minimize his vices. Rather than conceding Trump’s demolition of public standards of honesty and decency, his supporters pronounce him a little rough around the edges. His racial bias is dismissed as straight talk or rhetorical excess. His testing of constitutional boundaries is an excess of zeal. His cruelty and crudity are, when you get used to them, just part of the show.

But if, as I suspect, Trump’s deception, indecency, racism, viciousness and lawlessness are uniquely dangerous to our democracy, his enablers will find their deal more difficult to explain.

— Michael Gerson is a columnist with Washington Post Writers Group.