New York CNN Business  — 

More than 15 million viewers tuned in for part one of the 2020 presidential election’s first primary debate on television Wednesday night.

The Nielsen ratings reflect enormous interest in the presidential race – with millions of people tuning into NBC, MSNBC and Telemundo to size up the candidates who want to beat President Trump next year.

And these ratings don’t even include streaming viewership on YouTube, Twitter and other sites.

The 15.3 million total from Nielsen combines the viewership on the NBC broadcast network, MSNBC, and the NBC-owned Telemundo network, which carried the debate in Spanish.

This trifecta of TV viewing options, plus intense interest in the Democratic primary, nearly set a new ratings record for Democratic party primary debates.

The record was set in October 2015, when 15.5 million viewers tuned in to CNN for the first primary season debate between Hillary Clinton and Bernie Sanders.

A few months later, in January 2016, a Clinton and Sanders debate on NBC averaged 10.2 million viewers.

In the run-up to Wednesday night’s debate – the first of two this week – NBC executives privately said they’d be surprised to top 10 million viewers. It’s the summertime, they said, and those debates in the 2016 cycle happened later in the election season, when more voters were paying attention to the race.

Well, Wednesday’s ratings indicate that many voters are already paying very close attention.

The NBC-produced telecast suffered from a series of technical glitches, which the network took steps to address on Thursday, lest anything happen during night two.

Part two of the debate is likely to draw an even bigger audience because there will be bigger names on stage, including the two highest-polling candidates, Joe Biden and Bernie Sanders.

Wednesday’s debate ratings still fell far short of the Trump-fueled records for Republican primary debates that were set in 2015. Trump’s first time on the debate stage, in August 2015, helped attract 24 million viewers to Fox News. His second time, the following month, helped draw 23 million viewers to CNN.

All of these totals come from Nielsen’s television ratings system, counting viewers who are at home watching on TV sets.

The vast majority of big event viewing still happens that way, but online streaming is a growing factor as well. Wednesday’s debate was live-streamed on YouTube, Facebook, Twitter, and NBC’s own web sites.

The streaming totals are apples and oranges, not directly comparable to Nielsen ratings data, but NBC said live streams of the debate were also very popular.