The television audience for Tuesday's U.S. vice presidential debate between Republican Mike Pence and Democrat Tim Kaine is expected to be 40 million to 50 million - in line with previous such matchups, according to media reports on Wednesday.
The Hollywood Reporter, citing preliminary Nielsen and network data from the four main U.S. broadcasters, said the debate scored a 13.2 household rating.
That would translate into a total TV audience of around 51 million when final numbers from cable and other channels are released by Nielsen later in the day. That is about the same as the viewing figure for the 2012 vice presidential encounter between Democrat Joe Biden and Republican Paul Ryan.
CNN calculated that the final audience would be in the 40-50 million range.
Last week's first debate between presidential candidates Republican Donald Trump and Democrat Hillary Clinton was watched by a record 84 million TV viewers.
None of the figures for the debates include those who watched online, through social media, or in bars and restaurants.
Vice presidential debates have traditionally attracted smaller TV audiences, with the exception of the 2008 encounter between Biden and Republican Sarah Palin, which set a record for a VP debate of 69.9 million viewers.
Tuesday's 90-minute face-off between Pence and Kaine, broadcast live across 10 U.S. TV channels, was the only debate between the vice presidential contenders before the Nov. 8 election.
The two spent most of their time attacking each other's running mates but neither appeared to deliver a knockout punch.
(Reporting by Jill Serjeant; Editing by Frances Kerry)