PHILADELPHIA >> Longtime environmental lawyer and anti-vaccine activist Robert F. Kennedy Jr. said today he’ll run for president as an independent and drop his Democratic primary bid, adding a wrinkle to a 2024 race heading toward a likely rematch between President Joe Biden and former President Donald Trump.

Speaking today from Philadelphia’s Independence Mall, where America’s founding documents were adopted, Kennedy said there is a “rising tide of discontent” in the country and said he wants to make a “new Declaration of Independence” — from corporations, the media and the two major political parties.

“I’ve come here today to declare our independence from the tyranny of corruption which robs us of affordable lives, our belief in the future, and our respect for each other,” Kennedy said. “But to do that I must first declare my own independence. Independence from the Democratic Party and from all other political parties.”

Kennedy, a member of one of the most famous Democratic families in politics, was running a long-shot primary bid and has better favorability ratings among Republicans than Democrats. It’s unclear whether GOP support would translate to a general election when Kennedy would also be running against Trump. Allies of both Biden and Trump have at times questioned whether Kennedy would be a spoiler against their candidate.

“The truth is, they’re both right,” Kennedy said in his speech. “My intention is to spoil it for both of them.”

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 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.

Hundreds of supporters gathered for Kennedy’s remarks, at times chanting, “RFK, all the way!” Campaign signs teased a potential new slogan: “Declare your independence.”

Among Kennedy’s fans in the crowd were several voters who said they don’t identify as Democratic or Republican and view Kennedy as a truth teller and a breath of fresh air.

“He tells it how it is,” said Julia Hill, a 23-year-old student from New Jersey. “He doesn’t sound like a politician.”

Other supporters, such as Brent Snyder, a disabled veteran from south Philadelphia, said they had voted for Trump in the past but were looking for a change.

“The last couple years I’ve been noticing the Republican Party’s been going a way I didn’t like,” Snyder said. “Not that I agree with everything that’s happening to Trump, but I think right now he has more baggage than his country needs. The division right now is just terrible. We need someone to bring both sides together to make us work.”

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

“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.”

Today’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.

Kennedy has spent weeks accusing the DNC of “rigging” the party’s primary against him and threatening that he might need to consider alternatives.

In campaign emails and videos, he blasted the DNC’s decision not to host debates between Biden and other candidates and railed against the committee’s plan to give South Carolina rather than Iowa or New Hampshire the leadoff spot on the primary calendar this election cycle.

“If they jam me, I’m going to look at every option,” he said in September at a New Hampshire barbecue held by Republican former Sen. Scott Brown.

Far-right and anti-vaccine influencers close to Kennedy also sent strong signals on social media suggesting he should or would leave the Democratic Party. Last month, Joseph Mercola, an influential anti-vaccine doctor who is allied with Kennedy, ran a poll on X, formerly known as Twitter, asking if Kennedy should quit the party.

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.

Associated Press writers Michelle Smith and Will Weissert contributed to this report.