(Adds comments from debate historian, background)
By Lisa Richwine
LOS ANGELES, Sept 30 (Reuters) - The first U.S. presidential debate between Republican President Donald Trump and Democratic rival Joe Biden attracted 13% fewer television viewers than the record-setting one four years ago, according to Nielsen data released on Wednesday.
An estimated 73.1 million people tuned in to the chaotic face-off on Tuesday night across 16 networks, down from the 84 million who watched the first debate between Trump and Democratic rival Hillary Clinton in 2016. That matchup had the highest total viewership in 60 years of U.S. presidential debates.
During 90 minutes marked by personal insults and Trump's repeated interruptions, Trump and Biden battled over the president's record on the coronavirus pandemic, healthcare and the economy.
The Nielsen numbers included people watching at home and at such venues as bars and restaurants. It also included some digital viewership through televisions connected to the Internet.
The figures do not capture the full extent of online viewing, which has grown in popularity as traditional TV audiences decline. The debate was streamed live on Twitter, YouTube, network websites and other digital platforms.
While the TV audience did not set a record, the size was impressive in an era of streaming media that has fractured viewership, said Alan Schroeder, a debate historian and professor emeritus at Northeastern University.
The debate ranked as the second-most-watched event this year behind only the Super Bowl's roughly 100 million viewers.
"There aren't that many of these big-ticket live programming events anymore that everybody watches together," Schroeder said.
Some people may have skipped the debate because Trump and Biden, a former vice president and senator, are well known to voters, Schroeder said. Living amid the coronavirus pandemic and other challenges also may have made the debate unappealing, he said.
"There is a lot of heavy stuff going on, and people are emotionally spent," Schroeder said. "The prospect of watching something that makes you feel worse is not enticing to a lot of people."
Fox News Channel attracted the biggest debate audience of any single network on Tuesday, with 17.8 million viewers. The event, the first of three presidential debates before the Nov. 3 election, was moderated by Fox News host Chris Wallace.
The group that manages U.S. presidential election debates said on Wednesday it would take steps to bring order to the final two contests between Trump and Biden, which are scheduled for Oct. 15 and Oct. 22.
(Reporting by Lisa Richwine; Editing by Howard Goller and Peter Cooney)
Our Standards: The Thomson Reuters Trust Principles.