Yet Kennedy’s upstart campaign has a long way to go to compete with the funding, support and experience that the Trump and Biden campaigns enjoy. His announcement Monday was delayed briefly when he arrived onstage only to find his speech was loaded upside-down in the teleprompter.

Monday’s announcement comes less than a week after the progressive activist Cornel West abandoned his Green Party bid in favor of an independent White House run. Meanwhile, the centrist group No Labels is actively securing ballot access for a yet-to-be-named candidate.

Aware of the risk that Kennedy could pull votes away from Republicans, Trump allies have begun circulating opposition research against Kennedy designed to damage his standing among would-be conservative supporters.

The Republican National Committee published a fact sheet before Kennedy’s speech titled “Radical DEMOCRAT RFK Jr.” that lists times he supported liberal politicians or ideas. The document also listed times he supported conspiracy theories about COVID-19 or “stolen-election claims” related to the 2000 and 2004 presidential elections that Democrats lost to President George W. Bush. Trump continues to promote the disproved theory that his loss to Biden was the result of a stolen election.

Biden’s allies so far have dismissed Kennedy’s primary campaign as unserious. Asked for comment ahead of the announcement, a Democratic National Committee spokesman responded with an eye roll emoji. The DNC declined to comment Monday.

Four of Kennedy’s eight surviving siblings put out a joint statement denouncing his candidacy and saying his announcement saddened them.

“The decision of our brother Bobby to run as a third party candidate against Joe Biden is dangerous to our country,” it read. “Bobby might share the same name as our father, but he does not share the same values, vision or judgment.”

Tony Lyons, co-founder and co-chairman of American Values 2024, the super PAC supporting Kennedy, dismissed those comments as “part of a strategy to discredit him.”

“At his family dinner tables they would disagree about everything, and that’s what democracy looks like,” Lyons said. “Families are allowed to disagree.”

While Kennedy has long identified as a Democrat and frequently invokes his late father, Sen. Robert F. Kennedy, and his uncle President John F. Kennedy on the campaign trail, he has built close relationships with far-right figures in recent years. He appeared on a channel run by the Sandy Hook conspiracy theorist Alex Jones and headlined a stop on the ReAwaken America Tour, the Christian nationalist road show put together by Trump’s former national security adviser Michael Flynn.

Polls show far more Republicans than Democrats have a favorable opinion of Kennedy. He also has gained support from some far-right conservatives for his fringe views, including his vocal distrust of COVID-19 vaccines, which studies have shown are safe and effective against severe disease and death.

Kennedy’s anti-vaccine organization, Children’s Health Defense, currently has a lawsuit pending against a number of news organizations, among them The Associated Press, accusing them of violating antitrust laws by taking action to identify misinformation, including about COVID-19 and COVID-19 vaccines. Kennedy took leave from the group when he announced his run for president but is listed as one of its attorneys in the lawsuit.