Kristen Welker, the debate’s moderator, began the night with a plea for civility.
“Please,” she instructed the men standing before her, “speak one at a time.”
For the most part, Ms. Welker got what she wanted.
In a high-stakes debut overseeing a presidential debate — taking charge of a candidate matchup that proved a bucking bronco for the last moderator, Chris Wallace of Fox News — Ms. Welker, an NBC anchor and correspondent, managed to restore order to a quadrennial institution that some believed could not be tamed.
Mr. Wallace himself said on Fox News: “Well first of all, I’m jealous. I would’ve liked to have been able to moderate that debate and get a real exchange of views instead of hundreds of interruptions.”
No doubt, she benefited from Trump 2.0: a calmer president arrived onstage Thursday, a contrast with the candidate who derailed the proceedings in Cleveland last month. And she had a technological assist in the form of muted microphones, a novelty installed to keep the exchanges between Mr. Trump and Joseph R. Biden Jr. from going from civics to chaos.
But in a poised and crisp performance, Ms. Welker, 44, succeeded where Mr. Wallace got walloped. Battle-tested by years of covering the Trump White House, she parried with the president and cut him off as needed; Mr. Trump, eager to shed voters’ memories of his unruly performance last month, mostly acquiesced.
Ms. Welker — the first Black woman to moderate a general-election presidential debate since Carole Simpson of ABC in 1992 — entered the evening facing an onslaught of attacks from Mr. Trump, who earlier this week called her “terrible.”
Little of the pressure showed onscreen. Ms. Welker was polite but firm in guiding the discussion, offering chances for brief rebuttals but also taking control when the candidates threatened to go on a harangue, repeatedly urging, “We need to move on.”