SO THIS is how it was to end: a septuagenarian con-man flanked by four victims of sexual assault, real or alleged, trying to intimidate his opponent by dredging up old accusations against her husband, Bill Clinton. That pre-debate Facebook Live broadcast by Donald Trump, which combined farce, dystopia and reality-TV in three tawdry minutes, presaged the tone of the encounter that followed. As it turned out, his second confrontation with Hillary Clinton, at a town-hall style event in St Louis, did not signal the end of Mr Trump’s presidential bid. It may not lead to the headlong disintegration of the Republican Party, another outcome predicted in advance. Instead a hairline crack may have opened in the American republic itself.

In the light of events of the past few days, Mr Trump’s misjudgment in tweeting about a beauty queen’s non-existent sex tape already seems quaint. (“I’m not unproud of it”, he said of his social-media habit, suggesting that his small-hours calumnies were evidence of his fitness to cope with crises.) In his first opportunity to address the bigger scandal that has upended his campaign, through an opening question about whether the candidates set a good moral example, he failed to do so. It was only when pressed directly on the recording of him bragging, in 2005, about groping women’s genitals, that Mr Trump grudgingly described his remarks as “locker-room banter”. “Nobody has more respect for women than I do,” he insisted. Mrs Clinton set the furore in the context of the litany of insults he has dished out to other people and groups. “This is not who we are,” she said of their country. “We are great because we are good.”

Because of that tape, Mr Trump’s pre-debate predicament was unprecedented. Over the weekend Republican bigwigs, including Senator John McCain, un-endorsed him in droves, a mini-stampede that had the air of a medieval court’s chaos when a king seems mortally ill (with added Twitter). Mr Trump’s basic strategy was to scorch the earth and Mrs Clinton with it. Especially at the beginning of the evening, when his own behaviour was under discussion, he interrupted her relentlessly, also badgering the moderators, Anderson Cooper and Martha Raddatz, who generally performed creditably. He tried to humiliate Mrs Clinton by again bringing up Bill’s accusers, whom he had brought into the hall. And then Mr Trump said that, as president, he would appoint a special prosecutor to investigate Mrs Clinton’s infamous e-mail habits as secretary of state, and other putative offences. When she expressed relief that someone with a temperament like his was not in charge of the law, he said, “Because you’d be in jail.”

If that exchange took place in a foreign country, American diplomats would be denouncing it. It ought to be regarded as the evening’s most important moment, and its most shameful: the violation of a democratic principle that distinguishes free polities from authoritarian ones.

And yet, to Mr Trump himself, and to many of his fans, it would have merely sounded like a reprise of the chant—“Lock her up”—that is popular at his rallies. That echo is telling: his ambition seemed to be to shore up his base rather than to extend it. Had the latter been his goal, he might, for example, have been conciliatory towards a Muslim questioner rather than patronising her, or thought of something to say about African-Americans that didn’t involve crime and poverty. Unlike Mrs Clinton, he made no effort personally to engage with audience members. Mostly he hammered at his main themes: Islamic State (IS), which he mentioned repeatedly, and his supposed plans to close tax loopholes exploited by tycoons such as him, while “bigly” using his beautiful knowledge of the tax code to help the middle class. (In fact his ruinous proposals would favour the rich enormously.)

He made a couple of passable quips and managed a decent response to a corny, tail-end question about what he liked in Mrs Clinton, even if his answer—that she never quit—contradicted his claim that she lacked the stamina to be president. (She said she admired his children.) On the substance of foreign policy, one of the issues raised in the time left-over after groping, tweeting and e-mails, his ignorance would have been laughable had it not been so terrifying. “Maybe there is no hacking,” he said of Russia’s apparent penetration of the Democratic National Committee’s servers. “I know nothing about Russia,” he said of his alleged links with Vladimir Putin, an accomplished locker-up of political opponents whose strength Mr Trump has praised. “Russia is new in terms of nuclear,” he mystifyingly averred, loping around the stage like a manic zoo animal. He talked up the roles of Russia, Iran and Bashar al-Assad in fighting IS, saying that, on Syria, he disagreed with his running-mate, Mike Pence, who had failed to defend him over the tape.

Invitation to the gutter

If Mr Trump’s predicament at the start of the debate was parlous, Mrs Clinton’s was delicate. Debating him in this mood is a bit like negotiating with Russia’s foreign minister. He confronted her with “an absolute avalanche of falsehoods”, as she put it afterwards, the lies superseding each other so relentlessly that addressing all of them would have been impossible. In effect he invited her to take a roll in the gutter with him—inadvisable, as Marco Rubio can testify. Stoop down or back down, the thug’s perennial one-two: whatever response she mounted, the terms were set by him.

The path she and her advisers chose was to ignore his accusations against her husband. She coped reasonably well when her description of some of Mr Trump’s backers as “deplorables” came up. “My argument is not with his supporters,” she said, “it’s with him.” (“She has tremendous hate in her heart,” Mr Trump dramatically maintained.) For all the practice she has by now had, she was less convincing on the question of her e-mails, as well as on comments she once made, newly relayed by WikiLeaks, about having both public and private policy positions. Overall, after an assured start, hers was a stolid, defensive performance.

Meaning, altogether, that Mr Trump and his party seem lumbered with each other—though the idea of forcing him off the ticket may never have been more than a fantasy. His threats and boorishness are unlikely to have won many new voters, especially not women. But, equally, the cost of disavowing him may remain too high for many Republicans to risk it. Unlike the groping tape, this debate seems unlikely to have altered the shape of the race.

All the same, it was a telling, lamentable milestone in America’s politics. Mr Trump had already shattered taboos surrounding decency, honesty and intellectual incoherence. With his threats against Mrs Clinton he took a step down a dark road that should frighten every American.

Dig deeper:

Donald Trump boasts of groping women (October 8th 2016)

The first presidential debate: A win for Hillary Clinton (September 27th 2016)