Why don’t Trump’s humiliated enablers just quit?

We’re all familiar by now with the reasons advanced for why elected Republicans shrivel like dry houseplants whenever they are asked to distance themselves from the president.

They fear primary challengers. They dread his Twitter wrath. They like the judges.

All true as far as it goes. And we might add that partisanship has reached radioactive levels — what with the siloing of information sources, the “big sort” in geographical choices, and so forth.

But pause for a moment over the people who work directly for President Donald Trump.

Why do so few of them quit? The turnover rate in this administration has set records, but with the exception of James Mattis and John Bolton, remarkably few have walked out. (For what it’s worth, Trump contends that he fired both Mattis and Bolton.)

After Bolton’s departure, Trump crowed that “we have 15 candidates” for national security adviser. “Everyone wants it badly, as you can imagine.” And why would that be?

Because it’s key to keeping America safe? Because it carries great responsibility and opportunities to make the world more stable and secure?

“It’s great,” says the president “because it’s a lot of fun to work with Donald Trump.”

Thus does the job of national security adviser to the president of the United States get transformed into a game show slot.

The truth is that Trump is among the worst bosses in the world. He has tantrums, hurls insults and maintains a level of chaos that makes a Tilt-A-Whirl seem calm.

But none of that seems to faze Trump’s appointees, who have frequently accepted humiliation at his hands.

This week’s New York Times account of Trump’s behind-the-scenes fulminations about immigration illustrate the pattern. Dressing down his Homeland Security secretary, Kirstjen Nielsen, Trump demanded that she shoot down drones without legal authority.

When she pushed back, he sneered: “Kirstjen, you didn’t hear me the first time, honey. Shoot ‘em down. Sweetheart, just shoot ‘em out of the sky, O.K.?”

Bob Woodward’s book, “Fear” offers similar examples. He called his attorney general, Jeff Sessions, “mentally retarded. He’s this dumb Southerner.”

After Rudy Giuliani turned in a TV appearance that Trump judged insufficiently sycophantic, he jibed: “Rudy, you’re a baby. I’ve never seen a worse defense of me in my life. They took your diaper off right there. You’re like a little baby that needed to be changed. When are you going to be a man?”

He told Wilbur Ross that he didn’t trust him to negotiate because “you’re past your prime.”

He called Reince Priebus “weak” and gave him the nickname “Reincy.” And Axios has reported that when acting chief of staff Mick Mulvaney proposed a compromise in a budget meeting, he barked “You just f---ed it all up, Mick.”

If they won’t even stand up straight and assert their own dignity, it’s not surprising that they shrink from vindicating the honor of the United States and the rule of law.

If more of Trump’s people had resigned rather than silently assented to a presidency that displayed contempt for law, Trump might not be facing impeachment now.

According to the Times account on immigration policy — since confirmed by several other news outlets including Fox — Trump repeatedly called for shutting down the entire U.S./Mexico border; told aides to take the land along the border even without legal authority and promised to pardon them if they got into trouble; suggested filling a moat with snakes and alligators; demanded an electrified fence with spikes; and proposed that migrants who throw rocks be shot.

When told that was not possible, he revised it to shooting them in the legs.

The staffers gingerly noted that some of these things were illegal, and then dutifully trotted off to prepare moat cost estimates. Nielsen bleated, “I know you’re frustrated.”

Again and again, those surrounding Trump have taken to subterfuge (Gary Cohn snatching papers off the Resolute desk), or anonymous New York Times op-eds to proclaim their patriotic role in restraining the wilder impulses of the commander in chief.

But they do not protest that this administration is lawless. They don’t resign. They don’t go public. They wait to be fired and then insulted, and thereby reinforce the president’s perception that there are no guardrails.

Mona Charen is a senior fellow at the Ethics and Public Policy Center.

Send letters to letters@suntimes.com