While there were fellow narcissists among his forebears, was there a single nihilist like Trump? I doubt it, and so the current waters are in fact uncharted, because the ship of state has a sort of madman at its helm.

That he’s fighting back by impugning his critics’ motives, stonewalling investigators and carping about the media shouldn’t disturb anyone, not if we’re being grown-ups. Richard Nixon, confronted with his impeachment, thrashed and seethed. Clinton assembled a war room in an effort to outwit his adversaries. That’s the nature of politics. That’s the right of the accused.

But in the mere week since a formal impeachment inquiry was announced, Trump has already gone much farther than that and behaved in ways that explode precedent, offend decency and boggle the mind. We’re fools if we don’t brace for more and worse.

For grotesque example, he has suggested — repeatedly — that government officials who tattled about his crooked conversation with the Ukrainian president are spies who deserve to be executed. Had any other president done that, many Americans would speak of nothing else for the next month.

But from Trump, such a horror wasn’t even surprising, and it competed for attention with so many other outrages that it was dulled, the way so much of his unconscionable behavior is. When you churn out a disgrace a minute and no one expects anything nobler, you’re inoculated by your own awfulness.

He has taken his vilification of the media to new depths, content on this front, as on others, to pump Americans full of a toxic cynicism so long as he profits from it. He and his handmaidens have disseminated distortion after distortion, lie upon lie, including the claim that deep-state officials tweaked the criteria for whistle-blowers just so that someone could ensnare him.

They have instructed Americans not to believe their own eyes, their own ears, their own intelligence. They mean to put truth itself up for grabs, no matter the fallout.