The first presidential debate was watched by more than 80 million television viewers, according to early figures released by Nielsen on Tuesday, putting the clash between Hillary Clinton and Donald Trump on track for the biggest audience since televised debates began in 1960.
Preliminary figures from 12 national networks showed an average viewership of 83.8 million, ahead of the 80.6 million that tuned in to the 1980 debate between President Jimmy Carter and Ronald Reagan, the previous record-holder.
The estimated size of the audience is expected to be revised by Tuesday evening, when Nielsen announces a more definitive count.
But an estimate of about 80 million would edge out the 1998 finale of "Seinfeld," which attracted about 76 million viewers, even if it falls just short of Super Bowl numbers and the 105 million who watched the finale of "M.A.S.H."
Viewers who watched Monday's debate on live-streaming services were not included in this tally. Nor were those who watched on C-SPAN, which is not rated by Nielsen.
The audience represented a significant jump over the first encounter in 2012 between President Barack Obama and Mitt Romney, which drew 67.2 million viewers.
On cable, Fox News brought in the most viewers, with an average of 11.4 million, according to the early ratings. NBC News was the highest-rated broadcast channel, with an average of 18.2 million viewers.
Anticipation ran high for Monday's debate, moderated by Lester Holt of NBC, and social media services reported heavy activity during the 95-minute event.
By Tuesday morning, Holt's minimalist performance had drawn plaudits from some journalists and darts from conservative critics in Trump's camp, who accused the moderator of going soft on the Democratic candidate and failing to ask questions about the Clinton Foundation and the Benghazi attack.
"Moderator Steps in to Save Clinton," read a headline on Breitbart News on Tuesday. Rudy Giuliani, a close adviser to Trump, said that the candidate ought to reconsider attending the next two debates unless he receives promises "that the journalist would act like a journalist and not an incorrect, ignorant fact checker."
The second debate is scheduled for Oct. 9. The candidates will be asked questions in a town hall format, moderated by Martha Raddatz of ABC and Anderson Cooper of CNN.