A broad coalition of the Kennedy family will endorse President Biden on Thursday at a campaign rally in Philadelphia, pointedly rejecting one of their own in Robert F. Kennedy Jr., the independent candidate who many Democrats believe poses a significant threat to Mr. Biden’s re-election chances.
Among the relatives of Mr. Kennedy expected to back Mr. Biden are his siblings Joseph, Kerry, Rory, Kathleen, Maxwell and Christopher. The Biden campaign released a list of 15 Kennedys set to appear at the rally, but it said other family members would endorse the president as well. Kerry Kennedy will introduce Mr. Biden at the rally, the campaign said, and Joe Kennedy III, Mr. Kennedy’s nephew and a former Democratic congressman from Massachusetts, will do so at a second event.
The show of force will send the clearest signal yet that America’s most storied Democratic family is deeply fearful that one of its own could tip the 2024 election to former President Donald J. Trump, and hopes to use its influence to try to stop him.
Many family members have previously expressed strong disapproval of Mr. Kennedy’s candidacy, voicing anguish about his promotion of conspiracy theories and confusion about why he is challenging a Democratic president they admire. Like many Democrats, they worry that he could help Mr. Trump win if he draws even a small number of votes away from Mr. Biden in the battleground states — contests that were decided by tens of thousands of votes in 2020.
Mr. Trump is likely to remain the main target of attacks at the Philadelphia event, but the symbolic repudiation of Mr. Kennedy will not be subtle.
“We can say today, with no less urgency, that our rights and freedoms are once again in peril,” Kerry Kennedy is expected to say, according to excerpts from her speech shared by the Biden campaign. “That is why we all need to come together in a campaign that should unite not only Democrats, but all Americans, including Republicans, and independents, who believe in what Lincoln called the better angels of our nature.”
The family has telegraphed its intentions: Last month, members visited Mr. Biden at the White House for St. Patrick’s Day, sharing a photo of him with a large group of them. “From one proud Irish family to another — it was good to have you all back at the White House,” Mr. Biden wrote on social media.
Members of the Kennedy family also denounced an ad that a super PAC supporting Mr. Kennedy ran during the Super Bowl. The ad closely resembled a spot supporting John F. Kennedy, his uncle, during his 1960 bid for the White House.
With the election months away, and Mr. Kennedy still pursuing access to the ballot in many states, it’s hard to know whether he would draw more votes from Mr. Trump or Mr. Biden’s camp. But polls suggest that Mr. Trump’s base of support is much more fixed than Mr. Biden’s, meaning it’s possible that some of the president’s voters could be open to an alternative.
The Democratic Party has put together a team of lawyers aimed at tracking Mr. Kennedy’s threat, especially in battleground states. The group will also seek to counter other potential spoilers such as Cornel West, a progressive academic seeking the presidency, and the Green Party.
Democrats have already watched the collapse of one third-party effort they had nervously eyed: The centrist group No Labels, after seeking to set up a moderate politician with national recognition as an alternative to Mr. Biden and Mr. Trump, announced early this month that it would abandon its attempt.
Mr. Kennedy holds a smorgasbord of policy positions not easily categorized by ideology. He has expressed liberal views on abortion, the environment and income inequality, but has also promoted false theories about the safety of vaccines and pushed arguments that are more common on the right.
This month, he questioned the Justice Department’s effort to prosecute those who rioted at the Capitol on Jan. 6, 2021, downplaying the severity of the attack. His campaign also fired a consultant who had suggested that supporting Mr. Kennedy would help Mr. Trump defeat Mr. Biden.
Still, Mr. Trump has signaled that he, too, sees Mr. Kennedy as potentially attracting voters away from his campaign. He posted on social media last month that Mr. Kennedy was more “radical Left” than Mr. Biden, casting him as a liberal Democrat in disguise. Yet Mr. Trump has also privately expressed intrigue with the idea of choosing Mr. Kennedy as his running mate — a notion that those close to him consider unrealistic and that Mr. Kennedy himself rejected.
Mr. Biden’s rally in Philadelphia is the final major stop in a three-day swing through Pennsylvania. During the trip, he laid out his economic and tax agenda, repeatedly attacking Mr. Trump as wealthy, out of touch and an enemy of working people.
Members of the Kennedy family who appear at the rally are expected to invoke Robert F. Kennedy, Mr. Kennedy’s father.
“I can only imagine how Donald Trump’s outrageous lies and behavior would have horrified my father, Robert F. Kennedy, who proudly served as attorney general of the United States, and honored his pledge to uphold the law and protect the country,” Kerry Kennedy will say, according to her prepared remarks. “Daddy stood for equal justice, human rights and freedom from want and fear. Just as President Biden does today.”
After Mr. Biden speaks, Kennedy family members will make calls to voters and knock on doors, the Biden campaign said.