Trump and Harris Have Agreed to Debate on Sept. 10, ABC Says

The debate is on.

Vice President Kamala Harris and former President Donald J. Trump will face off in a televised prime-time matchup on Sept. 10, ABC News said on Thursday, setting up the latest crucial moment in an already unpredictable presidential campaign.

The 90-minute debate is expected to be held in Philadelphia, according to two people with knowledge of the plans. The ABC anchors David Muir and Linsey Davis will serve as moderators. The debate will probably be held without a live audience, but the exact format and ground rules are still being determined, the people said.

In one sense, the announcement maintains the status quo: Mr. Trump agreed months ago to debate President Biden on ABC on that same date. But the Republican nominee wavered on that commitment after Mr. Biden withdrew from the race, arguing that he had not agreed to those terms with Ms. Harris.

This year’s previous debate, in June, was perhaps the most consequential in the 64-year history of televised presidential matchups. Mr. Biden’s shaky and diminished performance set off a panic among Democrats that ultimately led to the president ceding his spot atop his party’s ticket.

More than 51 million Americans watched that debate live, the sort of mass gathering that is vanishingly rare in a fractured media age. The coming ABC telecast could attract an even larger audience, given that it will be the first time that Ms. Harris and Mr. Trump meet face-to-face on a debate stage.

The extraordinary events of recent weeks, including Mr. Biden’s withdrawal and an assassination attempt on Mr. Trump, have prompted many Americans to refocus on a presidential election that, until June, was shaping up as a rerun of the 2020 race. The ABC debate will most likely be a post-Labor Day kickoff moment of sorts for the campaign’s final two-month stretch.

Mr. Trump said at a news conference on Thursday that he would debate Ms. Harris on two other occasions, at events hosted by NBC News and Fox News. But the Harris campaign has not agreed to those debates, which were not part of the original debate schedule that Mr. Biden and Mr. Trump had agreed upon in May.

NBC News is in active discussions with both campaigns about a potential debate, including one on Sept. 25, but Ms. Harris has not committed, according to a person familiar with the discussions. The Harris campaign has also not agreed to a debate hosted by Fox News.

Ms. Harris, after speaking at a campaign event in Michigan on Thursday, told a reporter that she was “looking forward” to the debate on Sept. 10. “I hear he’s finally committed to it,” she said of Mr. Trump.

The ABC debate was negotiated with the campaigns by John Santucci, the executive editorial producer of the network, and Rick Klein, its Washington bureau chief. Mr. Trump’s campaign managers, Chris LaCivita and Susan Wiles, negotiated terms with the network.

Brian Fallon, a senior adviser for communications, played a lead negotiating role for the Harris campaign, according to the people with knowledge of the conversations. When Mr. Biden was still a candidate, that role was primarily occupied by the advisers Ron Klain and Anita Dunn.