Kennedy family members endorse Biden over RFK Jr.

More than a dozen members of the Kennedy family endorsed President Joe Biden for a second term Thursday, passing over family member Robert F. Kennedy Jr.

"We want to make crystal clear our feeling that the best way forward for America is to re-elect Joe Biden and Kamala Harris to four more years," Kerry Kennedy said in remarks announcing the endorsement at a campaign event in Philadelphia.

She made the endorsement on behalf of 15 Kennedy family members at the Martin Luther King Recreation Center alongside five of RFK Jr.’s other siblings: Rory Kennedy, Joseph Kennedy II, Kathleen Kennedy Townsend, Christopher Kennedy and Maxwell Kennedy Sr.

The Kennedy family has stepped up its involvement in the Biden campaign, working to lift Biden's odds as Democrats worry that Robert F. Kennedy Jr.'s bid could pose a spoiler risk that could hand the election to former President Donald Trump.

Former Rep. Joseph Kennedy III, the independent candidate’s nephew, said in an interview that he believes his uncle’s “candidacy poses a threat to the country that I love and the values that I hold.”

“I believe that his candidacy is likely to divert support away from President Biden and end up increasing support for Donald Trump,” he said.

The endorsement has been “months in the making,” according to a source familiar with the Biden campaign’s planning, who added that family members came forward to “do something to show they’re united by the president."

Robert F. Kennedy Jr. said on X: "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."

Kennedy claimed that "many of my family members are working on and supportive of" his presidential bid but did not specify which ones.

Joseph Kennedy III, who now serves in the Biden administration as special envoy to Northern Ireland, said the family endorsement is intended to blunt third-party support that could “siphon votes” from the president.

“We want to be able to make that case not just for the risk that Bobby’s candidacy shows but because of who Joe Biden is, what Joe Biden has done and what Joe Biden will do with four more years in office," he said.

Joseph Kennedy III acknowledged “challenging” feelings involved in the endorsement while noting that “it’s something we believe has to be done.”

“Bobby knows that we stand by him as a family member, while also being able to clearly communicate that his candidacy poses a risk to the country that we love,” the younger Kennedy said.

Kerry Kennedy appeared to echo that sentiment in her speech Thursday.

“We can say today, with no less urgency, that our rights and freedoms are once again in peril,” she said. “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.”

Kerry Kennedy directly attacked Trump and invoked her father, Robert F. Kennedy.

"I can only imagine how Donald Trump’s outrageous lies and behavior would've horrified my father, Sen. 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," she said before she compared her father's commitment to equal justice and human rights to Biden's.

In his own remarks, Biden called it an “incredible honor to have the support of the Kennedy family.”

Biden also joined members of the Kennedy family at a grassroots organizing event where he was introduced by Joseph Kennedy III. The president delivered remarks to local supporters and volunteers.

The campaign said members of the Kennedy family are also taking part in voter outreach by making calls and knocking on doors.

Members of the Kennedy family have praised Biden and boosted images of family members posing with him, such as a St. Patrick's Day photo depicting three generations of the Kennedy family with him.

Likewise, Biden describes Robert F. Kennedy as a political hero "who inspired him early in his career to leave corporate law to become a public defender, and then go on to run for public office," the Biden campaign said. Biden also has a bust of the elder Kennedy in the Oval Office.

Some members of the family have been more direct in their criticism of Robert Kennedy Jr., such as when Stephen Kennedy Smith referred on social media to what he called his cousin's "misguided stands on issues, his poor judgement, and tenuous relationship with the truth.”

Rory Kennedy said in an MSNBC interview this month: "I love my brother, and it pains me to come out against him. But I am very concerned with the stakes in this election."

"I'm concerned that his campaign and running for office as an independent is going to lead to Trump's election," she added.

Robert Kennedy Jr. responded to family members' criticism of his campaign this month, telling CNN's Erin Burnett, "I don't know anybody in America who's got a family who agrees with them on everything." He has reiterated that he loves his family and that he understands "why they don't like me running."

The campaign intentionally kept the event to immediate family members, such as several of the candidate’s siblings, a member of the large political family said.

The family member referred to how RFK Jr. has previously deflected questions about his family’s criticisms of his campaign.

“The message is crystal clear that Bobby’s own brothers and sisters are endorsing the president,” the person said.

Joseph Kennedy III was sympathetic to the security concerns that his uncle has raised regarding his denied request for Secret Service protection. The younger Kennedy said he was not aware of the specific threat assessments, but “I would want my uncle, just like anybody else that’s running for office, to make sure that they have the safety and security that they need to be able to run a campaign.”

Polling indicates that Biden and Trump are headed for a neck-and-neck race — and a high-profile third-party candidate, such as Kennedy, could further shake up both candidates' prospects. If the presidential election were held in March and the candidates were Biden, Trump and Kennedy, Kennedy would get about 16% of the vote, according to a Reuters/Ipsos poll.

This article was originally published on NBCNews.com