Some 73 million people tuned in to the first debate between US President Donald Trump and his White House challenger Joe Biden.
The TV viewership for Tuesday's clash was lower than the 2016 debates, but final streaming counts are pending.
The 2016 showdown between Mr Trump and Hillary Clinton broke TV records, pulling in 84 million viewers.
That one shattered the previous viewership record of 80.6 million set in the 1980 Reagan-Carter debate.
On Tuesday night, around 73.1 million people tuned in on 16 networks for the first primetime political duel between the White House contenders, according to Nielsen.
Mr Trump on Wednesday responded to the preliminary numbers by saying "some day these Fake Media Companies are going to miss me, very badly".
HIGHEST CABLE TELEVISION RATINGS OF ALL TIME. SECOND HIGHEST OVERALL TELEVISION RATINGS OF ALL TIME. Some day these Fake Media Companies are going to miss me, very badly!!!— Donald J. Trump (@realDonaldTrump) September 30, 2020
Though official streaming numbers for the debate have yet to be released, YouTube livestreams from just the Wall Street Journal, Fox News, CBS and ABC, for example, racked up over 20 million views combined.
Many other media outlets streamed the debate on YouTube. How many people listened on the radio or other formats is also unclear.
The next election debate will be between the running mates: Vice-President Mike Pence and Senator Kamala Harris on 7 October in Salt Lake City, Utah.
Mr Trump and Mr Biden will return to the stage two more times, on 15 October in Miami, Florida, and 22 October in Nashville, Tennessee.
Election day is on 3 November.
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