Washington (AFP) - Eight million people watched Hillary Clinton and her Democratic rivals debate at the weekend, fewer than half the number of Americans who tuned in to the most recent Republican showdown, Nielsen announced Tuesday.

The figure was only slightly lower than the 8.5 million who saw the Democrats' mid-November debate, and sharply less than the 15.8 million who watched the debut Democratic showdown in October.

It was also just 44 percent of the 18.1 million who watched the most recent Republican debate last Tuesday, according to television ratings firm Nielsen.

The latest Democratic showdown, hosted by ABC News, was perhaps the least inviting scheduled time for any presidential debate of the 2016 cycle to date. It was the final debate of 2015.

Clinton, Senator Bernie Sanders and Maryland's former governor Martin O'Malley squared off on a Saturday night at the height of the Christmas shopping rush, and on the debut weekend of the latest movie in the "Star Wars" franchise, which drew record audiences.

Republican critics have mocked the Democrats for their scheduling, saying the party is keen to suppress viewership because they do not want to expose frontrunner Clinton to challenges about her record.

The Republicans have held five debates, averaging 18.5 million viewers for each event.

Democrats by contrast have held three debates averaging 10.8 million viewers each.