Presidential hopeful Hillary Clinton and Bernie Sanders shake hands after the first Democratic presidential debate in Las Vegas, Nevada on October 13, 2015. (AFP)
More than 15 million people watched the debut Democratic debate of the 2016 US presidential campaign, a Democratic record but fully nine million fewer than the first Republican clash, CNN announced.
The Las Vegas showdown between former secretary of state Hillary Clinton, independent Senator Bernie Sanders, and three others drew 15.3 million viewers, debate host CNN said Wednesday, surpassing expectations of media experts who had predicted viewership in the single digit millions.
While the figure marked record viewership for a Democratic primary debate, it was a far cry from the 24 million people who tuned in to Fox News on August 6 for the first Republican clash of the cycle, featuring the party's frontrunner Donald Trump and nine challengers.
That was by far the highest rating of any presidential primary debate.
CNN hosted the second Republican debate, in mid-September, an event which drew 22.9 million viewers, the biggest-ever audience in CNN's 30-year history.
Television ratings firm Nielsen was to release its official viewership numbers for the Democratic debate later Wednesday.
No one had expected blockbuster viewership for the Democrats, who featured Clinton and Sanders along with three others who are barely registering in the polls: former Maryland governor Martin O'Malley, former senator Marine veteran Jim Webb, and Lincoln Chafee, the ex-governor of Rhode Island.
The ratings would undoubtedly have been higher if Vice President Joe Biden, who for months has weighed the prospects of a late entry into the race, were on stage Tuesday night.
CNN even reserved a spot for Biden in the off chance he would show up, and continually posted images of the empty lectern, an indication the cable network was concerned about audience interest.