Independent presidential candidate Robert F. Kennedy Jr. speaks at an event in Oakland, Calif. on March 26.

Josh Edelson/AFP via Getty Images

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Josh Edelson/AFP via Getty Images

Independent presidential candidate Robert F. Kennedy Jr. speaks at an event in Oakland, Calif. on March 26.

Josh Edelson/AFP via Getty Images

More than a dozen members of the Kennedy family will endorse President Biden’s reelection bid on Thursday — formally turning their backs on one of their own, Robert F. Kennedy Jr., who has launched his own independent run for office.

Kennedy, the son of Robert F. Kennedy and the nephew of former President John F. Kennedy, has a slim shot of winning in November, but a third-party candidate with a legendary Democratic surname has the potential to draw votes away from Biden.

At Thursday’s event in Philadelphia, Biden will be joined by Kennedy’s sister Kerry Kennedy and nephew Joseph Kennedy III, who are expected to speak. Other close family members will join them on stage.

“President Biden has been a champion for all the rights and freedoms that my father and uncles stood for,” Kerry Kennedy will say, according to excerpts of her prepared remarks released by the Biden campaign.

After the event, members of the family will knock on doors and make calls for Biden, according to the campaign.

The Kennedy family has long been a part of Democratic politics, and many prominent members have already been very critical of Robert F. Kennedy Jr.’s candidacy. Kennedy has promoted baseless conspiracy theories related to vaccines.

Kennedy’s campaign did not responded to a request for comment from NPR on the endorsement, but said on social media that “many of my family members are working on and supportive of” his campaign.

Kennedy raised hackles within his family after a political action committee supporting his campaign ran a Super Bowl ad that drew from his uncle’s 1960 presidential campaign, using the jingle, “Kennedy for Me.” He later apologized to them.

The Kennedy family said they are focused on reelecting Biden, who has cited Robert F. Kennedy Sr.’s political career as an inspiration for his own.

“We can say today, with no less urgency, that our rights and freedoms are once again in peril,” Kerry Kennedy will say, according to excerpts of her remarks.

“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,” she will say.