There were no technical snafus, dropped video feeds or any of the other on-air nightmares that had kept Democratic officials up at night. Besides a few mistimed cues here and there, the country’s first virtual convention on Monday — equal parts telethon, pep rally and Zoom therapy session — made its way smoothly to TV sets around the nation.
Fewer TV sets than four years ago, though.
Live television viewership of the opening night of the Democratic National Convention fell roughly 25 percent from 2016, according to Nielsen, with MSNBC emerging as the clear winner among the major networks.
About 19.7 million people watched the proceedings on TV from 10 to 11:15 p.m., the portion featuring speeches by Senator Bernie Sanders and Michelle Obama, the former first lady. Four years ago, about 26 million people tuned in for the Democrats’ first night in Philadelphia.
The Nielsen figures do not include online and streaming viewers, a rapidly growing chunk of the American mass media audience. Younger viewers, in particular, have grown accustomed to watching live events on news websites and services like YouTube. Cable and satellite TV subscriptions have been falling for years.
But there are few reliable ways to measure streaming audiences, and big TV networks remain a key vehicle for the candidates, Joseph R. Biden Jr. and President Trump, to reach a wide swath of voters, especially older ones.
Monday’s viewer patterns also demonstrate, rather starkly, the degree to which political partisanship has been ingrained in Americans’ decisions about what news to watch, and what to skip.
MSNBC, which is hugely popular with liberals, attracted the biggest audience of any network on Monday with 5.1 million viewers, nearly doubling its average audience at 10 p.m.
Fox News is the most-watched cable news network, and this summer its conservative stars have out-rated everything else on television in prime time. But on Monday, when Fox News switched from “Hannity” to the Democrats’ convention, its viewership dropped. About 2.1 million people tuned in, down from the average of 3.4 million who watch Laura Ingraham’s 10 p.m. show.
Without flag-draped delegates and decorative balloons, the virtual event bore little resemblance to pomp-filled conventions of the past. Instead of a stage, the spectacle originated from a windowless control room in Milwaukee — the original host city, until the coronavirus forced an end to those plans — where producers juggled dozens of video feeds and segments.
The M.C., the actress Eva Longoria, spoke from a closed studio set in Los Angeles. Mr. Sanders beamed in from Burlington, Vt. Ms. Obama recorded her speech at her family’s home on Martha’s Vineyard — a fact highlighted by party officials on Tuesday after some viewers wondered why she did not mention Senator Kamala Harris, who was chosen as Mr. Biden’s running mate after Ms. Obama filmed her remarks.
In terms of ratings, the Big Three broadcast networks — ABC, CBS and NBC — had a particularly tough night.
Collectively, the three lost about 42 percent of their live audience from 2016, with a particularly steep drop among younger viewers. (The overall cable audience also fell, but by less.) ABC had the biggest total audience among the broadcast stations, with 2.4 million viewers.
CNN’s overall audience was off 24 percent from 2016, but it was Monday’s best-performing network among viewers ages 25 to 54, the most closely watched advertising demographic in the TV news industry. CNN drew about 1.5 million of those younger viewers.