Donald Trump and Alicia Machado Photo: Steve Eichner/Getty Images

Before the first presidential debate, the defining confrontation of the general election was an inspiring speech by Khizr Khan, a Muslim-American Gold Star father. Khan’s speech was delivered before prime time, and its unexpected power might have been wasted had Donald Trump not taken the bait by repeatedly attacking Khan and his wife for days afterward. During the closing moments of Monday night’s debate, Clinton provided another Khan moment, and Trump, once again, could not help but reveal his own ugliness.

Clinton had been signaling her intent to focus on Trump’s longtime habit of humiliating women based on their appearance. A few days before, her campaign released an ad counter-posing some of his most infuriating comments about women with images of adolescent girls looking at themselves:

It is clear that Clinton planned to create this moment in the debate, because the question did not arrive organically. Trump had been talking about Iran, and moderator Lester Holt was trying to bring up the final question, when Clinton interrupted to spring her trap. Here is how the exchange begins:

HOLT: We are at — we are at the final question.

CLINTON: Well, one thing. One thing, Lester.

HOLT: Very quickly, because we’re at the final question now.

CLINTON: You know, he tried to switch from looks to stamina. But this is a man who has called women pigs, slobs, and dogs, and someone who has said pregnancy is an inconvenience to employers, who has said …

TRUMP: I never said that.

CLINTON: … women don’t deserve equal pay unless they do as good a job as men.

TRUMP: I didn’t say that.

Trump has already interrupted Clinton to deny his statements twice before she brings up the point she intends to drive home:

CLINTON: And one of the worst things he said was about a woman in a beauty contest. He loves beauty contests, supporting them and hanging around them. And he called this woman “Miss Piggy.” Then he called her “Miss Housekeeping,” because she was Latina. Donald, she has a name.

TRUMP: Where did you find this? Where did you find this?

CLINTON: Her name is Alicia Machado.

TRUMP: Where did you find this?

CLINTON: And she has become a U.S. citizen, and you can bet …

TRUMP: Oh, really?

CLINTON: … she’s going to vote this November.

TRUMP: Where did you find this?

You can easily see why Clinton’s campaign decided this was the perfect anecdote to display his grotesque personal qualities. It contains several elements all at once. There is Trump’s lecherous habit of creeping around beauty contestants, which is its own deep vein of gross behavior. There is the cruel reduction of women to their appearance. And there is the anti-Latina racism.

But what truly made the set piece work was Trump’s response, which Clinton could not have scripted better if she tried. Unlike the previous allegations, he did not deny them, but instead burst out — three times! — “Where did you find this?” I have seen villains in Disney movies presented with damning evidence react this way, but I have never seen an actual human being do it, until now.

Then Clinton capped it off by noting that Machado plans to vote — which was the same response generated by Khan’s speech:

As soon as Khizr Khan finished his speech, "register to vote" spiked as a Google search. pic.twitter.com/0HZbBuCWwR — Nate Goldman (@NateGoldman) July 29, 2016

Here it was again, the perfectly selected victim fighting back against Trump by voting, precisely the action Clinton hopes to encourage. Clinton’s campaign immediately capitalized by releasing a new web ad with Machado telling her story. And Trump, despite the entire Republican Party beseeching him to walk away from the Khan fight and never engage in attacks against ordinary Americans, insisted in a Fox & Friends interview on attacking Machado for being too fat:

You can watch the Fox hosts cringe as Trump launches into the diatribe, and then, as they gently try to steer him away, insists on returning to the subject. They can see him destroying himself again, in real time, in exactly the way they begged him to stop doing earlier in the summer, yet they cannot stop it.

Life rarely works out in such a simple and dramatically perfect way. Terrible human beings usually know how to conceal their terribleness. Even a villain as impulsive and egotistical as Trump has the benefit of an entire political party and associated media apparatus throwing itself behind the task of concealing his hideous character through Election Day. Trump, however, is not only a horrible human being but a congenitally incompetent one.