WASHINGTON (AP) — Donald Trump stands on the threshold of what two ex-presidents called the “profound disgrace” of impeachment, a permanent stain on his legacy.

Of what Alexander Hamilton set out in the Federalist Papers as the apt remedy for “the misconduct of public men.”

Or what Trump mockingly dismisses as impeachment lite.

The leader who has sliced a scythe through institutions and thrives in disruption stands unrepentant as a splintered nation prepares to impeach a president for only the third time in history.

Yet the weight of history is at hand.

So is a certain numbness among we the people as a process once granted the gravity of exorcism — an awakening from a “national nightmare” — plays out for a public that consumes daily provocations from this unusual president and can read only so many tweets in a day.

The U.S. may be witnessing the trivialization of impeachment for charges that are anything but trivial, said Jeffrey A. Engel, a presidential historian and lead author of a book on impeachments that has found its way into the hands of senators as they prepare to hold a January trial on the House’s expected indictment.

“Our extraordinary partisanship has trivialized it,” he said in an interview. “We’re in a remarkably partisan time.”

Look closely, though and you can see that Trump, for all his shrugs and dismissive taunts, knows he is on the verge of making a list of presidential infamy. Impeachment, he said in a lengthy letter to House Speaker Nancy Pelosi on Tuesday protesting his innocence, is a “very ugly word.”

Trump is to join Bill Clinton, impeached 21 years ago for lying under oath about sex, and Andrew Johnson, impeached 151 years ago for defying Congress on Reconstruction.

Impeachment is not likely to engender an impulse of contrition for Trump, and it might not even sully his political future. For every American who thinks Trump is a constitutional criminal, another American thinks he’s being railroaded.

Yet, for all time, there will be no erasing the ultimate presidential black mark.

‘’Make no mistake, the judgment of history does matter,” two former presidents, Republican Gerald Ford and Democrat Jimmy Carter, wrote in an op-ed after the House impeached Clinton in 1998.

Ford and Carter were, in turn, the presidents who picked up the shattered pieces of Richard Nixon’s presidency after Watergate, the searing episode by which all presidential corruption scandals have been measured since. Nixon only avoided impeachment because he quit on the cusp of it.

In their joint article, Ford and Carter pleaded for Congress to skip Clinton’s trial in the Senate because, they said, profound disgrace from the House impeachment would follow him forever. They wanted him censured instead.

The Senate went ahead with the trial and acquitted him, just as it did with Johnson and as it is highly likely to do with Trump.

Clinton and Nixon were halfway through their second terms, approaching the twilight of their presidencies when they faced the threat of impeachment. Trump is standing for reelection, giving his impeachment the flavor of the kind of dramatic showdown he professes to relish.

Raging at his accusers, the Democrats, while stonewalling them, Trump says he takes no responsibility for all that has transpired and is yet to come.

“Zero, to put it mildly,” he said Tuesday, accusing Democrats of “cheapening” the very idea of impeachment.

To presidential historian Robert Dalleck, the consequences are far-reaching.

“The miracle of America has been that it’s been able to hold together,” he said. “To sink into this national division that exacerbates these differences and tension is to open the way to the collapse of American democracy, I think. “

During the Clinton impeachment, constitutional scholar Michael Gerhardt was the only expert witness called by both parties to testify. Democrats summoned him again in the House Judiciary Committee hearings in the Trump impeachment.

“The president is really denying the legitimacy of the Constitution and of inquiry,” he said in an interview, tracing what he sees as distinctive about this president and this impeachment.

“President Clinton accepted the legitimacy of the Constitution, and he didn’t object to the inquiry. He did object to the merits. Trump has described his own conduct as ‘perfect’ as well as beyond the law and impeachment, something neither Clinton nor Nixon claimed.”

This president, Gerhardt said, “seized the divisiveness and just makes it worse.”

To be sure, the Clinton impeachment unfolded with a script flipped from today as Democrats railed about an attempted “coup,” just as Republicans now assail the Trump impeachment as a “sham.”

Yet within the ranks of each party, some members agonized over what to do and sagged as if under a great weight.

As the House debated impeachment 21 years ago Wednesday, Republican Rep. Thomas Davis of Virginia said his heart wasn’t in the effort to remove a president and “‘I didn’t want to get out of bed this morning.” Another Republican, Rep. Tom Campbell of California, delivered his argument in favor of impeachment in a near whisper and close to tears.

The impeachment took savagely partisan turns. Yet Donald Ritchie, an official Senate historian then and for many years, said key norms were respected as the upper chamber tried and acquitted the Democrat.

Procedural rules were approved unanimously, he said, and everyone had a chance to speak. “The Senate operated in a very dignified, fair and impartial manner.”

Democrats acknowledged Clinton’s wrongdoing, just as Republicans acknowledged Nixon’s culpability as the damning evidence became overwhelming a quarter century earlier.

In the Clinton case, many Democratic lawmakers wanted their president to be censured, a lesser punishment but also one for the history books. They argued that Clinton’s lying to a grand jury to cover personal misbehavior did not meet the standard for removal from office. But they did not deny the underlying facts.

Similarly in the Nixon crisis, Ritchie said, “Everybody was listening to the evidence.”

Engel is director of the Center for Presidential History at Southern Methodist University. In his multi-author book, “Impeachment: An American History,” he details the Founding Fathers’ debate over how and when to invoke that extraordinary power against a president’s malfeasance.

He said the refusal by Trump and Republican lawmakers in the House hearings to acknowledge the basic facts of this case distinguishes the Trump impeachment from the proceeding against his predecessors. “We’ve not had a president so unconcerned with basic facts and truth as this president,” he said.

Trump has stuck to his story that he had a “perfect” phone call with Ukraine’s president and asserted repeatedly that people only need to “read the transcript” to know of the call’s perfection.

But a rough transcript of the call reveals his explicit interest in having Ukraine’s leader announce an investigation into Trump’s potential reelection rival, Joe Biden, and into a baseless conspiracy theory that Ukrainians and Democrats colluded against his 2016 election.

Engel suggested people read another sort of rough transcript, too, from July 20, 1787, as delegates to the Constitutional Convention wrestled with the terms of impeaching a president.

“Shall any man be above Justice?” George Mason asked, according to the minutes. Benjamin Franklin suggested impeachment was a better alternative than assassination “for the regular punishment of the Executive where his misconduct should deserve it.”

James Madison thought impeachment “indispensable” for dealing with a president’s “incapacity, negligence or perfidy.”

“He might pervert his administration into a scheme of peculation or oppression,” he said, according to the minutes. “He might betray his trust to foreign powers.”

From such debate came the standard of treason, bribery or other high crimes and misdemeanors. In the era of Trump, that standard is on trial as well.