More than 67 million people tuned in to watch the chaotic presidential debate across the broadcast networks and three major cable news channels on Tuesday night, about a 10 percent decline from the first presidential debate four years ago, according to preliminary Nielsen figures.
In 2016, roughly 75 million people watched the inaugural matchup between Donald J. Trump and Hillary Clinton across those seven networks.
Final live television viewership figures for the debate between President Trump and Joseph R. Biden Jr., including tallies from other networks like PBS and Telemundo, will be released later on Wednesday by Nielsen.
In all, a record 84 million people watched the first debate between Mr. Trump and Hillary Clinton. When the final figures are in, Tuesday’s debate will exceed the 67.2 million who watched the first presidential debate in 2012.
The Nielsen numbers do not include people who streamed the event or watched it online, which is even more widespread now than it was four years ago.
Presidential debates, which air on at least a dozen networks, are typically among the most-watched telecasts of the year. The Super Bowl, which had about 100 million viewers this year, is one of the few events with wider reach. Election night coverage in 2016 was watched by 71 million television viewers.
This year’s Republican and Democratic National Conventions drew television audiences smaller than the ones they had in 2016, with a drop of about 25 percent for each. The declines for the conventions and the debate could be explained by the shift in viewing habits, from traditional TV to streaming platforms and websites — but no outside group credibly measures the online viewing audience.
The downturn may also result from the fact that Mr. Trump’s presence in a political arena — which helped shatter ratings records throughout the 2016 campaign — has become less of a novelty.
Tuesday’s showdown was the first time that Mr. Trump and Mr. Biden had squared off in a campaign that has entered its final stretch. Mr. Trump repeatedly interrupted Mr. Biden during his allotted speaking time and was not deterred when the moderator, Chris Wallace of Fox News, urged him to stop. At one point, an exasperated Mr. Biden said to Mr. Trump, “Will you shut up, man?”
“I’m just sad with the way last night turned out,” Mr. Wallace told The New York Times on Wednesday.
Viewers, however, did not appear to be turned off by all the cross talk. Audience figures on the broadcast networks and the three cable news channels grew in the first 30 minutes and peaked with an average of 68 million viewers between 9:30 and 9:45 p.m. Eastern time, according to Nielsen. Declines after that were relatively modest. Sixty-four million people were still tuned in to the seven top networks for the final few minutes of the debate, according to Nielsen.
About 17.8 million people tuned in to Fox News to watch the debate, by far the highest tally for any network. ABC, the only broadcast network to have an hour of pre-debate coverage, had an audience of 12.6 million, the second highest of any outlet.