NEW YORK — Nearly 20 million television viewers tuned in to Thursday's Democratic presidential debate. 

Nielsen says that was the biggest audience ever for a debate of Democratic candidates for president.

The feisty session was the first time that former New York City Mayor Michael Bloomberg met his competitors in verbal combat after blanketing the airwaves with ads. 

It was more than double the audience of ABC's Feb. 7 debate just before the New Hampshire primary. 

RELATED: Trump, Gardner hosting rally in Colorado Springs on Thursday

RELATED: VERIFY: Fact-checking the Las Vegas Democratic debate

RELATED: Bloomberg nabs three new congressional endorsements after debate debut

RELATED: Here's how the Nevada caucuses work and why we may not have a result Saturday

RELATED: Protesters interrupt Joe Biden at debate over immigration policies

Election 2020 Debate Candidates
From left, Democratic presidential candidates, former New York City Mayor Michael Bloomberg, Sen. Elizabeth Warren, D-Mass., Sen. Bernie Sanders, I-Vt.,former Vice President Joe Biden, former South Bend Mayor Pete Buttigieg, Sen. Amy Klobuchar, D-Minn., stand on stage before a Democratic presidential primary debate Wednesday, Feb. 19, 2020, in Las Vegas, hosted by NBC News and MSNBC. (AP Photo/John Locher)