Growing up in a proud Irish Catholic middle-class family, Joe Biden’s family idolized the Kennedys. They saw the Kennedys — successful, wealthy, attractive Irish Catholics — as the embodiment of the American Dream. Biden says Robert F. Kennedy Sr., whose bust sits in the Oval Office, inspired him to become a public defender and ultimately run for office.

“The Kennedys were, as a group, the people he patterned his life after,” said former senator Ted Kaufman (D-Del.), who was Biden’s longtime chief of staff and remains his close friend. “Not just his political life, but his life.”

So when the Kennedy family rallied behind Biden last week in Philadelphia with a full-throated endorsement of his reelection campaign, pointedly choosing him over one of their own — Robert F. Kennedy Jr., who is running as an independent — it was not just politically helpful. It was a hugely personal victory for Biden, too.

Privately, Biden told aides that Thursday was one of the best days of his campaign, according to people familiar with his comments who spoke on the condition of anonymity to discuss private conversations. The event included more than a dozen members of the extended Kennedy family, including six of Kennedy Jr.’s siblings, and Biden was particularly moved when they said the president was the candidate carrying on their family’s legacy.

Publicly, Biden was visibly touched by the fulsome endorsement by Kerry Kennedy, his rival’s sister.

“That was the most meaningful introduction I’ve ever gotten in my life, other than when my sister introduced me,” Biden said Thursday after her introduction.

The Kennedy family hopes their endorsement will help Biden politically. Kennedy Jr.’s independent presidential campaign threatens to siphon votes from Biden, increasingly worrying Democrats that he could meaningfully hurt the president’s chances of defeating Donald Trump. The outcome could hinge on a few thousand votes in key states, and many Democrats say they lost the White House in 2000 and 2016 due to such third-party insurgencies.

Inside the Kennedy family, Kennedy Jr.’s quixotic campaign has been painful, people familiar with their discussions said. Initially, when he was challenging Biden for the Democratic nomination, his family was frustrated — and made clear that they stood with Biden — but largely ignored the candidacy publicly. They were unconcerned about Kennedy Jr.’s impact on the election, since Biden was almost certain to defeat him the Democratic nomination.

But as an independent candidate who is winning ballot access around the country, members of the family have grown increasingly concerned about his ability to influence the election — and damage their family’s legacy.

“Nearly every single grandchild of Joe and Rose Kennedy supports Joe Biden,” Kerry Kennedy said in her introduction of Biden. “That’s right, the Kennedy family endorses Joe Biden for president.”

She later directly compared Biden to her father, the late Sen. Robert F. Kennedy (D-N.Y.).

“Daddy stood for equal justice, for human rights and freedom from want and fear,” she said, “just as President Biden does today.”

The Kennedy family occupies an unusual place in the U.S. political imagination. President John F. Kennedy was a youthful, charismatic president who energized a generation of Americans until his shocking assassination in 1963. His brother Robert, a more tortured figure, was seen by many Democrats as the embodiment of tragic idealism after his own assassination in 1968 as he campaigned for president.

Scandal has also followed the family, and while members of the next generation have also won political office, none have ascended to the heights of political and cultural influence of their parents. Yet the Kennedy mystique persists for many Democratic voters, especially older ones.

That backdrop is one reason the candidacy of Kennedy Jr. has thrown such a twist into the current presidential campaign. The son and namesake of the revered senator has embraced controversial, unfounded claims on everything including vaccines and the Jan. 6, 2021, attack on the U.S. Capitol — rattling many Democrats and, it seems, some of his own family members.

Several of those relatives have had pointed conversations with Kennedy Jr. about his candidacy, but to no avail, and many close to him say they do not believe he will drop out of the race. That understanding fueled the family’s desire to join in a public endorsement of Biden, the people familiar on their conversations said.

“This has not been easy for anybody, and I think what shouldn’t be lost on anybody is despite the framing of the event, that was not an easy thing for anybody to do given the dynamics of this race,” former congressman Joe Kennedy (D-Mass.), a grandson of the elder Robert F. Kennedy who now serves as Biden’s special envoy for Northern Ireland, said in an interview. “But it was an important thing to do.”

He, like other members of his family, declined to comment directly on his uncle’s presidential campaign. A number of the candidate’s family members have condemned Kennedy’s comments on vaccines and other matters, but they have been careful not to frame their endorsement of Biden as an explicit rebuke of their relative. Instead, they say it is a reflection of their belief there are only two possible outcomes in November: Biden wins, or former president Trump wins.

“Given the reality that we’re in, there are only two people that have the ability to win this race,” Joe Kennedy said. “There’s only two parties that have the structures in place to be able to win this race. So any additional candidate in that dynamic is taking support away from one side or the other.”

For his part, Kennedy Jr. has not commented on his family’s endorsement since the event occurred. Before his siblings gathered with Biden, however, he wrote on social media, “I hear some of my family will be endorsing President Biden today. I am pleased they are politically active — it’s a family tradition. We are divided in our opinions but united in our love for each other.”

At 81 years old, Biden has found that his own path — involving both enormous political success and immense personal tragedy — in some ways mirrors that of the Kennedy family.

After being steeped in Kennedy lore as a child, Biden found solace in the family’s embrace when he faced the death of those closest to him. A few weeks after he was elected to the Senate in 1972, and before he was even sworn in, Biden’s wife and daughter were killed in a car crash. His sons Beau and Hunter were injured, and Biden considered relinquishing his seat to take care of them.

But Sen. Edward M. Kennedy (D-Mass.), along with other colleagues, convinced Biden to stay. Kennedy helped Biden set up his Senate office, becoming a mentor and close friend.

“I know the president is somebody that has a deep value on family and puts a big premium on loyalty, and when you are there for somebody at their most vulnerable, he remembers it,” Joe Kennedy said about his family’s connection with Biden. “It’s that relationship that I think has had a huge impact on members in both families, particularly for an older generation. They’ve gone through immense loss, too, and so has he, so there’s a commonality there.”

In addition to Joe Kennedy, many other Kennedys work in Biden’s administration: Caroline Kennedy, the daughter of President John F. Kennedy, is ambassador to Australia; Victoria Reggie Kennedy, Edward Kennedy’s widow, is the ambassador to Austria; Katherine Kennedy Townsend, one of Kennedy Jr.’s siblings who stood onstage with Biden, previously worked in Biden’s Labor Department as an adviser on retirement and pension issues. (The two ambassadors cannot engage in political activity and were not included in Thursday’s endorsement event).

That Philadelphia rally, which was largely spearheaded by Joe Kennedy and Kerry Kennedy, came after family members made clear they wanted to publicly endorse the president. It took months to organize, given the family’s sprawling size. While there was some discussion of holding the event in Massachusetts, the Kennedys’ traditional home, family members decided against it because most of them no longer live in the state.

They Kennedys also wanted to campaign in a battleground state, and after the rally, some of then went door-knocking and met with Biden campaign volunteers in Philadelphia.

This month, nearly 50 members of the Kennedy clan gathered at the White House for the annual St. Patrick’s Day celebration, staying for a private tour of the Oval Office and posing for a photo with Biden in the Rose Garden. Biden and many of the Kennedys shared the photo on social media, the first implicit rebuke of Kennedy Jr.’s campaign by his family members.

But during that visit, just as in Thursday’s event, Kennedy Jr.’s presidential campaign did not explicitly come up, family members said.

“A lot of what was going in the Oval Office, people were talking to him about President Kennedy being there, and my father, and where he put the bust and why he likes to look at the bust of my father when he is making difficult decisions,” Kathleen Kennedy Townsend said.

She added, “We have a wonderful connection to Joe Biden. We love politics. We love this country. We love Ireland.”