Picking a president is always about personality, when you get right down to it. And this contest is between a candidate who wins votes by boasting about his business genius, and a woman whose headline quality is her nerdy work ethic. So the question going into tonight was, can the rich guy breeze his way through 90 minutes of debating the future of America—or can a wonk wrong-foot him?

Well, the first presidential debate of 2016 goes to the nerd—and she won it only about an hour into the debate.

The turning-point moment came during a heated exchange about race in America. Donald Trump was detailing his discussions with law enforcement officials, when he saw a dig he couldn’t resist: needling Hillary Clinton for staying off the trail in the last week.

“I’ve been all over the place. You decided to stay home, and that’s okay,” said Trump.

Clinton waited patiently—with that intensely calm blinking—while he finally wound up his rambling sentence—and then pounced.

“I think Donald just criticized me for preparing for this debate. And yes, I did,” Clinton said. “And you know what else I prepared for? I prepared to be president. And I think that’s a good thing.”

The audience at the Hofstra University auditorium defied the ban on noisemaking to cheer.

In that moment, Clinton pulled off a few things. First there’s the compelling analogy she drew. For the first hour of the debate, she handled questions firmly and cogently, while still managing to get under Trump’s skin by questioning his wealth and his honesty. Maintaining that calm slow-mo nod and rhythmic blinking, as Trump huffed, sniffed, squinted, and interrupted.

By likening her obvious success in the debate to her commitment to being president, Clinton reminded the voters she needs to reach of how hard she’ll work for them. The contrast she drew was similarly sharp: Trump’s retread of rally speeches shows he prepared hardly at all. She also lightly highlighted one of the nastier of Trump’s impulses, the sarcastic asides.

Clinton also owned her diligence, which is a quality that can sometimes come off as too goody-goody. That might ring familiar to women used to having to dumb down their participation in class or at work in order not to show up their male classmates and colleagues. Finally, the line was funny, capping off her composure and genuineness with the casual humor reminiscent of Barack Obama—which is about as presidential as you can get.

Editor’s note: An earlier version of this article had a headline based off a quote that was incorrectly transcribed. The quote has been corrected.