Seizing one of his biggest media moments ahead of the election in November, President Biden delivered a State of the Union address on Thursday that doubled as a campaign kickoff speech, presenting himself to Americans as a still-feisty leader prepared for the rigor of a grueling campaign.

Whether his pitch resonates with voters remains to be seen. But plenty tuned in to see what he was offering.

About 32.2 million people tuned in live to watch Mr. Biden’s speech, up 18 percent from last year’s audience of 27.3 million, the ratings agency Nielsen said on Friday.

The 66-minute-long appearance was Mr. Biden’s second-most-watched speech to Congress. His first, in 2021, attracted 26.9 million viewers, and about 38.2 million watched in 2022, days after the Russian invasion of Ukraine.

Mr. Biden’s next opportunity to command such a large audience is likely to be the presidential debates scheduled for the fall. Speeches at summertime political conventions do not usually draw more viewers than a State of the Union address.

The Nielsen numbers spanned 14 major cable and broadcast networks. The ratings do not account for many Americans who tuned in via streaming TV platforms, online news sites and social media posts. That group is a growing share of the total audience as viewers abandon traditional cable systems. But there is no agreed-upon metric to accurately measure online views.

Nielsen said about 74 percent of live TV viewers were 55 and older, about the same proportion as last year’s speech.

Fox News attracted 5.8 million viewers on Thursday, the largest live audience of any network. ABC was watched by about 5.2 million people, leading the three biggest broadcasters.

NBC was the top-ranked network among viewers ages 25 to 54, the most important demographic for advertisers in the TV news industry.

Aides to Mr. Biden appear to be gradually letting him out of a media cocoon after allies raised concerns about his limited public appearances. In particular, a decision by the White House to skip a traditional interview ahead of the Super Bowl set off alarm bells in Democratic circles.

The president is now embarking on a series of campaign stops. On Saturday, he is scheduled to tape an interview with Jonathan Capehart, a left-leaning host and commentator on MSNBC. The interview will be Mr. Biden’s first with a major television network since he spoke with Scott Pelley of CBS News in October.