Robert F. Kennedy Jr., a scion of one of the country’s most famous Democratic families, on Monday dived into the full embrace of a host of conservative figures who eagerly promoted his long-shot primary challenge to President Biden.

For more than two hours, Mr. Kennedy participated in an online audio chat on Twitter with the platform’s increasingly rightward-leaning chief executive, Elon Musk. They engaged in a friendly back-and-forth with the likes of Tulsi Gabbard, the former Democratic congresswoman turned right-wing commentator; a top donor to Gov. Ron DeSantis of Florida; and a professional surfer who became a prominent voice casting doubt on coronavirus vaccines.

Mr. Kennedy, who announced his 2024 presidential campaign in April, is himself a leading vaccine skeptic, and has promoted other conspiracy theories. Yet he has consistently hovered around 20 percent in polling of the Democratic primary, which the party has otherwise ceded to Mr. Biden.

On Monday, he sounded like a candidate far more at ease in the mushrooming Republican presidential contest.

He said he planned to travel to the Mexican border this week to “try to formulate policies that will seal the border permanently,” called for the federal government to consider the war in Ukraine from the perspective of Russians and said pharmaceutical drugs were responsible for the rise of mass shootings in America.

“Prior to the introduction of Prozac, we had almost none of these events in our country and we’ve never seen them in human history, where people walk into a schoolroom of children or strangers and start shooting people,” said Mr. Kennedy, who noted that both his father and uncle were killed by guns.

Mr. Kennedy said he now had “about 50 people” working for his campaign. Unlike Marianne Williamson, the other announced Democratic challenger to Mr. Biden, he does not appear to be aiming to appeal to Democrats who are ideologically opposed to the moderate president or are otherwise uneasy with renominating him. Instead, he has used his campaign platform — and his famous name — to promote misinformation and ideas that have little traction in his party.

Asked during the discussion by David Sacks, a top DeSantis donor who is also close to Mr. Musk, “what happened to the Democratic Party,” Mr. Kennedy spent nine uninterrupted minutes attacking Mr. Biden as a warmonger and claimed that their party was under the control of the pharmaceutical industry.

“I think the Democratic Party became the party of war,” Mr. Kennedy said. “I attribute that directly to President Biden.” He added, “He has always been in favor of very bellicose, pugnacious and aggressive foreign policy, and he believes that violence is a legitimate political tool for achieving America’s objectives abroad.”

The Democratic National Committee and Mr. Biden’s campaign declined to comment about Mr. Kennedy.

The event, which at its peak had more than 60,000 listeners, according to Twitter, at times felt as if Mr. Kennedy were interviewing Mr. Musk about his stewardship of Twitter, a platform that has lost more than half of its advertising revenue since the billionaire acquired it in October. For more than 30 minutes at the event’s start, the presidential candidate interrogated the tech mogul about releasing the so-called Twitter files, self-driving cars and artificial intelligence.

“These are really interesting topics for people, but I think a lot of the public would like to hear about your presidential run,” Mr. Musk said to Mr. Kennedy.

Mr. Kennedy, 69, is a longtime amplifier and propagator of baseless theories, beginning nearly two decades ago with his skepticism about the result of the 2004 presidential election as well as common childhood vaccines. His audience for such misinformation ballooned during the coronavirus pandemic.

On Monday, Mr. Kennedy repeated a host of false statements, among them:

• He said that after the Affordable Care Act of 2010, “Democrats were getting more money from pharma than Republicans.” An analysis by STAT News found that political action committees with ties to pharmaceutical companies gave more money to Republicans than Democrats in 14 out of 16 election years since 1990.

• He claimed, without evidence, that “Covid was clearly a bioweapons problem.” American intelligence agencies do not believe there is any evidence indicating that is the case.

• And as he blamed psychiatric drug use for the rise of gun violence in the United States, he contended that the gun ownership rate in the U.S. was similar to that of Switzerland. The United States had the highest civilian gun ownership rate in the world, at an estimated 120.5 firearms per 100 people, according the latest international Small Arms Survey. That was more than double the rate of the second-highest country, Yemen at 52.8, and much higher than Switzerland’s 27.6.