Mike Bloomberg‘s debut on the Democratic primary debate stage on Wednesday helped push its TV ratings into record territory, with nearly 20 million people tuning in to the telecast on NBC and MSNBC.

The two-hour debate was the most-watched in history for Democratic candidates, but fell far short of becoming the most-watched primary debate overall. That distinction still belongs to the August 2015 debate among Republicans, carried by Fox News and featuring another newcomer, Donald Trump; it drew 24 million viewers.

Mr Bloomberg, who has spent heavily on campaign ads but has otherwise been little seen on the campaign trail, was the main curiosity at Wednesday’s event in Las Vegas as well as the object of harsh attacks from his five fellow candidates. They challenged him on his record as New York mayor and his conduct as the founder and chief executive of his self-named media company. The reviews of Mr Bloomberg’s performance generally weren’t kind.

The telecast attracted an average of 19.66 million viewers between 9 pm and 11 pm Eastern time, according to Nielsen Media Research’s preliminary data. That figure exceeds the audience during the first Democratic debates in June, which set the previous high for the party’s candidates. The second night of that two-night debate was watched by 18.1 million people.

The viewing surge was a bit of good news for the Democratic National Committee, which had seen viewership drift downward for its officially sanctioned debates after the strong start last year. The low points were the fifth and sixth debates (of nine so far) in November and December, watched by just 6.6 million and 6.2 million people, respectively.

The Democrat challengers to Trump in 2020 Show all 25 1 /25 The Democrat challengers to Trump in 2020 The Democrat challengers to Trump in 2020 Bernie Sanders The Vermont senator has launched a second bid for president after losing out to Hilary Clinton in the 2016 Democratic primaries. 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Wednesday’s debate was the prime attraction on TV for the night, far surpassing the next most-popular programs, including “Survivor” (7.16 million viewers) on CBS and “The Masked Singer” on Fox (7.02 million).

NBC also said the debate attracted 13.5 million live streams, the highest figure during this election cycle (live streams aren’t comparable to TV ratings, which are averaged over the course of a program; the figure is a measure of how many times a video begins playing, even if only for a few seconds).

In addition to Mr Bloomberg, the candidates included former vice president Joe Biden, former South Bend, Indiana, mayor Pete Buttigieg, and Senators Amy Klobuchar, Bernie Sanders and Elizabeth Warren.