Yet the NeverTrumpers never scattered entirely, and thank heavens for that. Every political system will always have a conservative faction, and every healthy democracy needs that faction to be rooted in some combination of classical liberalism and moral traditionalism. Trump’s G.O.P., whatever its political fortunes, is the opposite: a nativist party led by a libertine.

At some level, conservatives know this. Trump knows they know it. Which explains why he has turned his sights on Never Trumpers: What despots and demagogues fear most is their followers developing a conscience.

No wonder the president chose to lambaste Lt. Col. Alexander Vindman as a “Never Trumper.” The combat veteran had the simple decency of being scandalized by what he heard from the president on the Ukraine phone call, and by what he knew of the discrepancies between what he heard on the call and the account of it released by the White House.

The decency of being scandalized is what being NeverTrump is centrally about, and why the movement remains important. It’s the opposite of the opportunism required to go along with the president because you might get something out of him.

It’s the same sense of scandal that led to the first significant G.O.P. revolt against Trump since John McCain turned his thumb down on Obamacare repeal in 2017: The suppurating disgust even pliant conservatives like Mitch McConnell and Lindsey Graham feel at Trump’s cavalier betrayal of the Kurds. It could motivate John Bolton (a born-again Never Trumper, along with John Kelly, Rex Tillerson, H.R. McMaster, Anthony Scaramucci and everyone else who made the mistake of working for this president) to deliver what may yet be the most devastating insider’s indictment of the president’s shameless shadow foreign policy.

And it helps explain why the president’s support with his base is slipping at last. A new poll finds Trump’s support among Republicans at 74 percent — an eight-point decline since September and the lowest since he was elected. Nearly one in five Republicans support impeachment and removal. So do 47 percent of independents. These numbers will not move in Trump’s favor if the truth about his “drug deals” (to borrow Bolton’s phrase) continues to come to light.

I doubt any of this will be sufficient to get at least 20 Republican senators to vote for Trump’s removal from office. But Trump knows that the number needed to spell his moral defeat on impeachment is four. If Mitt Romney, Susan Collins, Lisa Murkowski and one other Republican join the Democrats to convict, the political humiliation will be thunderous. And, as my colleague David Leonhardt has convinced me, it could devastate his re-election chances. If the administration thinks impeachment is such a political winner, they wouldn’t be fighting it this hard.

In the meantime, someone ought to print “Human Scum” on a limited-edition T-shirt. Given who said it about whom, it turns out to be a badge of honor.

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