Did President Biden cunningly rig the Super Bowl so the Kansas City Chiefs would win?

“I’d get in trouble if I told you,” Mr. Biden joked in his campaign’s inaugural post on TikTok, the Chinese-owned social media platform that has 170 million U.S. users but few high-level American politicians.

The video then cut to an image of the “Dark Brandon” meme — another attempt from the campaign to flip a right-wing conspiracy theory on its head.

Mr. Biden’s arrival to TikTok, and the lighthearted nature of his post, pointed to his ongoing attempts to rebuild his support among young voters. After weeks in which aides had floated that he would join the platform, his campaign pushed the button on its first video during the Super Bowl on Sunday night.

The 30-second clip featured the president dodging questions from an offscreen inquisitor.

Who would win the big game? (He dodged and noted Jill Biden’s fandom for the Philadelphia Eagles.)

Which Kelce brother did he prefer? (Again, a diplomatic response: “Mama Kelce.”)

And was he indeed responsible for a vast conspiracy theory floated on the far right positing that the White House and the N.F.L. had colluded so the Chiefs would win the game and somehow help his re-election campaign? (Cue “Dark Brandon.” Mr. Biden also shared an image of the meme on X shortly after the game, writing, “Just like we drew it up.”)

Joining TikTok is a sharp pivot for the Biden re-election campaign, which had officially maintained that it didn’t need its own TikTok account to reach voters and that it would work through influencers instead.

The move also carries some degree of risk: TikTok is owned by the Chinese company ByteDance and is banned on government devices in most states and at the federal level. Republicans especially, but also Democrats and national security experts, have raised concerns about the control China’s authoritarian government could wield over the platform’s data and content showed to Americans. TikTok has pushed back on those concerns.

The Biden campaign said on Monday that it was taking “advanced safety precautions around our devices and incorporating a sophisticated security protocol to ensure security.”

Such caution about the platform has contributed to the reluctance of politicians and their campaigns to join TikTok, despite the app’s growing influence. As of December, just 37 sitting members of Congress were on the app, and there were no official @POTUS, White House or Biden 2024 accounts, according to an analysis by The New York Times.

Among the Republican presidential candidates, only Vivek Ramaswamy had his own account. He dropped out of the race last month.

The app, once known for viral dance videos, has increasingly become a source of news and information, particularly for younger Americans. About 14 percent of U.S. adults said they regularly got news from TikTok last year, up from 3 percent in 2020, according to the Pew Research Center.

Last month, campaign officials celebrated when a TikTok video made by a North Carolina teenager whose home Mr. Biden visited drew millions of views on the platform.

Whether the Biden campaign can make the 81-year-old president look cool on the platform remains an open question. In the Sunday post, Mr. Biden wore khaki pants and a blue quarter-zip sweater with a microphone clipped to the zipper. The questions came from Rob Flaherty, a deputy campaign manager, according to a campaign official.

The post had received 4.5 million views by Monday morning, according to TikTok.

While TikTok does not allow paid political advertising, several campaigns have successfully used the app to build a rapport with potential voters and to help win races. Senator John Fetterman, Democrat of Pennsylvania, for example, counted TikTok among the tools he used to beat Dr. Mehmet Oz in the 2022 midterm elections.