The numbers are in: 51.3 million Americans tuned in live to watch Thursday night’s televised debate between President Biden and former President Donald J. Trump.
The prime-time bout, organized by CNN and simulcast on more than a dozen networks, was easily the most-viewed moment of the 2024 presidential campaign, the sort of mass civic gathering that is increasingly rare in a choose-your-own-news era of media. And the figure released on Friday by Nielsen, which mostly measures traditional TV sets, did not include the likely millions more who watched on digital news sites and social media platforms.
The size of the TV audience — similar to that for an N.F.L. conference championship game — could be grim news for the Biden campaign, given the shaky and stumbling performance by the president, which set off panic in the upper echelons of the Democratic Party.
But viewership was also down 30 percent from the first Biden-Trump debate in September 2020, which notched more than 73 million viewers. Nielsen said Thursday’s matchup in Atlanta was the lowest-rated general-election debate since the final meeting of George W. Bush and John Kerry in 2004.
Part of the decline can be explained by timing: The Biden-Trump debate occurred far earlier in the year than usual, well before many casual voters have become focused on the election. Overall TV audiences are smaller in the summertime, too, and the number of households with active cable subscriptions has dropped precipitously since 2020.
CNN, which hosted the debate (and supplied the moderators, Dana Bash and Jake Tapper), had the highest viewership of any network, although only just. About 9.5 million people watched live on CNN, compared with 9.3 million who watched on Fox News and 9.2 million on ABC.
CNN was the clear winner among adults 25 to 54, the most important group for advertisers. In the 10 p.m. hour, which included a round of post-debate analysis, Fox News pulled ahead of CNN in total viewers.
The TV audience for the debate skewed older; roughly two-thirds of viewers were over 55, Nielsen said. Those who tuned in to watch the candidates did not tune out: The live TV audience stayed roughly the same throughout the 99-minute telecast.
For CNN, which has endured a rocky period of management changes and sagging ratings, the debate was a much-needed shot in the arm. The network has fallen far behind its rivals; before Thursday’s debate, it was on track to record its lowest-rated month in prime time since 1991.
Whether another head-to-head presidential event occurs this year is an open question. The candidates have agreed to meet again on Sept. 10 for a debate sponsored by ABC. But Mr. Biden or Mr. Trump could choose to withdraw from that event depending on where the race stands after Labor Day.