The third debate was marked by Trump's refusal to commit to accepting the outcome of the election. (AP)
The final debate between White House contenders Hillary Clinton and Donald Trump on Wednesday attracted a bigger TV audience than last week's face-off, but is expected to be well below the record setting 84 million who watched their first encounter, according to early data.
Hollywood trade publications Variety and The Hollywood Reporter on Thursday cited preliminary Nielsen estimates as showing that the debate got a 39.7 overnight household rating in the nation's biggest cities.
The first Clinton-Trump face off in September scored a 46.2 overnight rating that translated into a total TV audience of 84 million - the largest in the history of US presidential debates.
Last week's second debate, which was broadcast opposite popular "Sunday Night Football," got a 37.2 early rating, and the total TV audience ended up being 66.5 million.
Final figures across all US networks that carried the debate live will be released by Nielsen later on Thursday.
The figures reflect only those who watched the debate on TV at home and do not include millions more who watched online, through social media or in bars and restaurants.
The third debate ahead of the November 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.
The early Nielsen figures showed that the biggest TV audience for Wednesday's debate was in Fort Myers and West Palm Beach in Florida, a key state in the election.
© Thomson Reuters 2016