Trump’s presidency was scary from the very start, when he summoned “American carnage” and hallucinated inauguration throngs. But the past several days have been something else: a clarifying, terrifying descent.

How low will Trump go? Leagues lower than you ever imagined, and probably several hundred feet below your current nightmares. Officials with Trump’s re-election campaign apparently plan to use “get over it” as a slogan on merchandise, but I think that the White House’s real new motto comes from Tacitus, a celebrated historian in ancient Rome: “Crime, once exposed, has no refuge but in audacity.”

That audacity animated Mulvaney. It was manifest when Trump publicly beseeched China to get in on the action and do its own investigation of Hunter and Joe Biden. It helps explain the decision — which, under intense pressure, he reversed on Saturday — to convene the G7 at Trump National Doral Miami, a gesture of such perverse defiance, such profound contempt, that it takes the breath away.

With the gaslighting logic that is his greatest gift, Trump is asserting that no real crook would be this nakedly, flamboyantly criminal, and he’s giving anyone in America who isn’t aboard the Trump train the middle finger. It, not his brain, is the body part with which he governs.

This is all about impeachment, to which he has responded — predictably — with a puerile rage. The first, second and third laws of Trumpian psychology are that for every action, there’s an unequal and hysterical overreaction, and ever since impeachment took on an air of probability, he has been overreacting all over the place.

He’s at his most dangerous when he’s most vulnerable and impotent, because he’s compelled to project command and potency. He has to convince everyone that he’s unflustered and unafraid.

That, as much as any promise to voters, motivated the disastrous pullout from Syria and abandonment of Kurdish allies. Precisely because it was what might undermine the loyalty of his Republican saviors and leave him exposed, he did it. It was a pantomime of fearlessness, a pretense of invincibility.