A total of 18.1 million viewers tuned into NBC News, MSNBC and Telemundo combined for Thursday night's Democratic presidential debate.
The figures make the event the second most-watched primary debate in television history and the largest on the Democratic side.
According to Nielsen Fast National Data, the event in Miami was also the second most-watched in the 25-54 demographic that advertisers covet, attracting 5.3 million viewers.
A majority of the viewers tuned to NBC on the broadcast side compared to cable channels MSNBC and Telemundo.
Ten candidates appeared in the debate, which grew fiery after Sen. Kamala HarrisKamala HarrisStefanik in ad says Democrats want 'permanent election insurrection' Live coverage: California voters to decide Newsom's fate Florida woman faces five years in prison for threatening to kill Harris MORE (D-Calif.) went after Joe Biden's record on civil rights. The former vice president has been the front-runner in the race, leading all national polls since launching his campaign in April.
Sen. Bernie SandersBernie SandersBriahna Joy Gray: Push toward major social spending amid pandemic was 'short-lived' Sanders 'disappointed' in House panel's vote on drug prices Manchin keeps Washington guessing on what he wants MORE (I-Vt.) and South Bend, Ind., Mayor Pete ButtigiegPete ButtigiegLGBT film festival to premiere documentary about Pete Buttigieg Pete and Chasten Buttigieg welcome twins Coalition urges Democrats to restore billion in transit funding MORE (D) also appeared in the debate, along with six other candidates. The event came on the heels of another Democratic debate featuring 10 other White House hopefuls the previous night.
Both debates were moderated by "NBC Nightly News" anchor Lester Holt, "Today" show co-host Savannah Guthrie, "Meet the Press" moderator Chuck ToddCharles (Chuck) David ToddIf .5 trillion 'infrastructure' bill fails, it's bye-bye for an increasingly unpopular Biden GOP governor: Biden's vaccine mandate 'increases the division' Manchin says he can't support Biden's .5 trillion spending plan MORE, MSNBC host Rachel MaddowRachel Anne MaddowRachel Maddow extends contract with MSNBC: reports OAN loses appeal in defamation lawsuit against Rachel Maddow Nunes sues MSNBC, alleging Rachel Maddow defamed him MORE and "Noticias Telemundo" and "NBC Nightly News" Saturday anchor José Díaz-Balart.
The most-watched primary debate in history occurred in August 2015 in the lead-up to the 2016 presidential election, when more than 24 million people tuned in to Fox News for the GOP event in Cleveland, Ohio.
That debate, which featured Donald TrumpDonald TrumpOhio Republican who voted to impeach Trump says he won't seek reelection Youngkin breaks with Trump on whether Democrats will cheat in the Virginia governor's race Trump endorses challenger in Michigan AG race MORE as a candidate for the first time, also attracted a record 7.9 million viewers in the 25-54 demographic.
The first debate on the Democratic side in the 2016 campaign season occurred in October 2015, when 15.5 million viewers tuned into CNN for an event that featured former Secretary of State Hillary ClintonHillary Diane Rodham ClintonAttorney indicted on charge of lying to FBI as part of Durham investigation Durham seeking indictment of lawyer with ties to Democrats: reports Paul Ryan researched narcissistic personality disorder after Trump win: book MORE and Sanders.