Carly Fiorina delivered the line that earned the most applause at the second Republican Presidential debate, momentarily silencing Donald Trump. PHOTOGRAPH BY MARK J. TERRILL / AP

It is a well-known rule of prime-time television that you don’t give away the plot or run the celebrity interview early in the show, so that people won’t tune out and go to bed. Ideally, you keep viewers on the hook until the last minute. But, when the show is a Republican political debate and it’s three hours long, it’s asking a lot for viewers to watch until the halfway point, let alone the end.

Evidently, the folks at CNN decided that an hour was about as long as they could keep people hanging. That was the point in the debate, which was held at the Ronald Reagan Presidential Library, in Simi Valley, California, when the host, Jake Tapper, asked Carly Fiorina to comment on Donald Trump’s recent offensive remarks about her appearance. (According to Rolling Stone, Trump said, after seeing Fiorina on television, “Look at that face! Would anyone vote for that? Can you imagine that, the face of our next President?”)

Until that point, the debate had gone pretty much as expected, with various candidates taking their shots at knocking Trump off his perch, and the seemingly indestructible New York businessman bluffing his way through without suffering much apparent injury. Tapper raised Rand Paul’s concern, expressed on CNN earlier in the week, about a man of Trump’s temperament having his finger on the nuclear button. (Trump replied, “My temperament is very good, very calm.”) Jeb Bush had accused Trump of using political donations to lobby for Florida to legalize casino gambling, and claimed that he had rebuffed Trump’s attempt. (“Jeb, don’t make things up. Come on,” Trump said, rebutting the notion that he’d wanted casino gambling there.) And Scott Walker, evidently unaware of Trump’s actual role on his long-running reality-TV show, said that we don’t need another apprentice in the White House. (Trump didn’t bother responding to that.)

Fiorina, though, bided her time. Offered an early opportunity to comment on Trump’s putative role as commander of America’s nuclear arsenal, she demurred, noting merely that he was “a wonderful entertainer.” The question of his fitness to be Commander-in-Chief would be one for the voters to answer, she said. A bit later, she made it clear that she had no doubt of her own C-in-C chops. Rather than negotiating with Vladimir Putin (as Trump has suggested he would), Fiorina said that she would rebuild the Sixth Fleet, reconstruct the American missile-defense system in Eastern Europe, and send thousands more troops to Germany. Russia was “a bad actor,” she averred, and Putin was “someone we should not talk to.”

That comment earned Fiorina some applause from an audience that appeared to have been drawn from the Hoover Institution/Cold War wing of conservatism, more than the Tea Party. But she didn’t receive nearly as much applause for that as for the response she gave to Tapper’s question about the Rolling Stone article, following another exchange between Trump and Bush, during which Trump emphasized that he’d heard something Bush had said. Looking levelly into the camera, Fiorina, the only female in the G.O.P. race, said calmly but forcefully, “Mr. Trump said that he heard Mr. Bush very clearly and what Mr. Bush said. I think women all over this country heard very clearly what Mr. Trump said.”

Doubtless, it was a line that Fiorina had rehearsed, but she delivered it beautifully, and it generated by far the biggest cheers of the night. Trump, for once, seemed somewhat at a loss for words, and his face, which was red all night—it was very hot onstage, and many other candidates were sweating, too—seemed to blush a little deeper. “I think she’s got a beautiful face,” he said, finally, “and I think she’s a beautiful woman.” It wasn’t an apology (Trump doesn’t do those), and it was greeted with near silence.

A bit later on, Tapper afforded Trump the opportunity to win back some points of his own, bringing up Fiorina’s record as chief executive of Hewlett-Packard. “The company is a disaster and continues to be a disaster,” Trump said, citing a study by a Yale professor that described Fiorina’s tenure at H.P. as one of the worst in corporate history. Fiorina stayed calm, though, and showed that she possesses political talents that appeared sadly lacking in her previous venture into electoral politics, an abortive 2010 run in California for the U.S. Senate. In particular, she demonstrated the invaluable ability to deliver whoppers with apparent sincerity. Dismissing the Yale study as the work of a Clintonite, she described her troubled time at H.P., which ended when the company’s board fired her, as a period of revenue growth, innovation, and desperate measures taken in desperate times. She even managed to slip in the fact that, on the day she was fired, Steve Jobs called her to commiserate. All Trump could manage was “I only say this. She can’t run any of my companies.”

After that, Trump seemed a bit deflated. (Admittedly, it could have been the heat.) And Fiorina, evidently seeking to portray herself as just as hawkish as any of the men surrounding her, laid it on a bit thick during a discussion of ISIS, saying that she would make sure that the U.S. military had fifty Army brigades, thirty-six Marine battalions, more than three hundred naval ships, and enough nuclear weapons to blow up the entire solar system. (I made up the last bit, but you get the idea: Jeane Kirkpatrick meets Dr. Strangelove.) By that stage, though, it probably didn’t matter. The television audience had dwindled, and the online pundits were already declaring Fiorina the winner—which, until the post-debate polls arrive, means she was the winner.

For many of the other candidates, it was a mixed night. Jeb Bush was more forceful than in the previous G.O.P. debate, but the most memorable things he said were that he smoked pot in college, would choose Margaret Thatcher if he had to select a woman to appear on the ten-dollar bill, and would make his Secret Service name Eveready, because, as he explained to Trump, who has accused him of listlessness, “It’s very high energy.” (This comment came in garbage time, and it earned him an ironic low five from the front-runner.) Ben Carson, who is the closest candidate in the polls to Trump, once again disappeared for long stretches, but in a debate that most voters, even Republican voters, will only watch via soundbites, this wasn’t necessarily a bad thing for him. He had a couple of strong moments, such as when he revealed that he had advised George W. Bush not to invade Iraq (earning him a high five from Trump, who also opposed the war), and when he affirmed, twice, that there is no evidence that vaccinations cause autism. (Carson even had the temerity, in front of a Republican audience, to suggest that there are moments when it makes more sense to rely on intellect than military force.)

Marco Rubio, once again, had some good moments, although probably not enough to dislodge him from the position of everybody’s second-favorite candidate. John Kasich, to his credit and, almost certainly, his own detriment, followed a rote assertion that the Iranian nuclear deal was a “bad agreement” with an attempt to defend the virtues of a multilateral approach to foreign policy. Chris Christie, the forgotten man of Trenton, sought to position himself as the adult in the room, admonishing Trump and Fiorina to stop quibbling about their business records and concentrate on the concerns of construction workers who don’t give a fig about their careers. (It must be noted, however, that Christie’s efforts to look serious weren’t helped when he said that his Secret Service security name would be True Heart. Evidently, he was unaware that True Heart is one of the Care Bears.)

Those were sidebars, though. The big story was Fiorina’s attempted takedown of Trump. “I think she’s a very nice person,” Trump said in an interview after the debate. We will have to wait and see if her performance has any lasting impact on the race.