By Jill Serjeant
(Reuters) - More than 68 million people watched the final debate between White House contenders Hillary Clinton and Donald Trump on TV on Wednesday, below the audience for their first encounter but potentially among the biggest ever recorded.
Nielsen data supplied on Thursday by Fox News, Variety and The Hollywood Reporter showed that about 38 million watched Wednesday night's debate on the four main U.S. networks, while more than 30 million tuned into cable TV channels.
The first Clinton-Trump face-off in September attracted a total TV audience of 84 million, the largest in the history of U.S. presidential debates.
Last week's second debate, which was broadcast opposite popular "Sunday Night Football," was seen by 66.5 million.
Final figures were likely to rise when data for smaller networks are included and totals are released by Nielsen later on Thursday.
The final numbers could put Wednesday's encounter in the top four most-watched U.S. presidential debates since Nielsen started collecting TV viewership figures for the encounters in 1976.
Nielsen data reflects only those who watched the debate on TV at home and did not include millions more who watched online, through social media or in bars and restaurants.
The third debate ahead of the Nov. 8 election was marked by Republican Trump's refusal to commit to accepting the outcome of the election if he loses to his Democratic rival, challenging a cornerstone of American democracy.
Wednesday's presidential election debate in Las Vegas was moderated for the first time by a journalist from Fox News, Chris Wallace. It brought in a leading 11.2 million audience for the Fox News cable channel, followed by broadcasters ABC and NBC with more than 10 million viewers each.
Second and third presidential debates have generally attracted smaller TV audiences because many voters have already made up their minds after a presidential campaign lasting more than a year.
(Reporting by Jill Serjeant; Editing by Frances Kerry and Jonathan Oatis)