Kennedys endorse Biden over their relative RFK Jr

Robert F Kennedy Jr on the campaign trail in California

More than a dozen members of America's most famous political family have endorsed President Joe Biden over their relative Robert F Kennedy Jr.

Mr Biden was joined by members of the Kennedy clan, which helped shape the modern Democratic Party, in Pennsylvania on Thursday.

The endorsement underlines the lack of support for Mr Kennedy Jr's independent bid to be president within his family.

He mounted his campaign after weighing a run for the Democratic nomination.

In Philadelphia, Mr Biden was introduced by Kerry Kennedy, Mr Kennedy Jr's younger sister.

In her remarks, Ms Kennedy did not directly mention her brother but said that there were only two candidates with "any chance of winning the presidency".

She compared Mr Biden to her father and touted the president's support for unions, Ukraine, and efforts to improve US infrastructure and reduce crime. She called Mr Trump "the most anti-democratic president in American history" and said he was spreading "dangerous conspiracy theories" that would have horrified her father.

"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," she said.

Former President Donald Trump is expected to face Mr Biden, a Democrat, in November as the Republican nominee.

A number of relatives have opposed Mr Kennedy Jr's campaign from the start, and members of the family, which has deep roots in Ireland, visited Mr Biden at the White House on St Patrick's Day.

In Philadelphia, several family members are door knocking or making calls for the Biden campaign. Among the group endorsing Mr Biden is Joe Kennedy III, a former congressman who serves as the Biden administration's special envoy to Northern Ireland for economic affairs.

Although the influence of the Kennedys has declined this century, few families have had such a marked effect on US politics. Mr Kennedy Jr counts a president and senator among his uncles, and in 1968 his father was assassinated while running for the Democratic presidential nomination.

Mr Kennedy Jr had a career as an environmental lawyer before leading the anti-vaccine campaign group Children's Health Defense, which saw its profile and donations soar during the Covid-19 pandemic.

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In a post on X, Mr Kennedy Jr wrote: "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."

He noted that several other family members are working for his campaign, which is managed by his daughter-in-law, Amaryllis Fox Kennedy.

Mr Kennedy Jr said his presidential run was about "healing America - healing our economy, our chronic disease crisis, our middle class, our environment, and our standing in the world as a peaceful nation."

Polls indicate Mr Kennedy Jr is the most popular of a number of third-party and independent candidates who also have entered the race, and could potentially pick up enough votes to affect the results in several states, although it's unclear whom he might hurt more - Mr Biden or Mr Trump.

His most immediate challenge in the race will be getting his name on the ballot. The campaign says it has met the requirements to qualify for the ballot in nine states, with efforts underway in most others.

On Thursday, the campaign said it had qualified in Michigan after Mr Kennedy Jr was nominated by the Natural Law Party - a minor party whose presidential candidate received less than 3,000 votes in the state in 2020.

In most states, qualifying as an independent candidate means collecting thousands of signatures. Experts say the process can cost millions of dollars. Mr Kennedy Jr's vice presidential running mate, Nicole Shanahan, recently gave the campaign $2m, according to an election filing.

The Democratic Party has already mounted a legal challenge, arguing that a political action committee supporting the Kennedy campaign is not allowed to help collect those signatures.

Democrats have also tried to link Mr Kennedy Jr to Mr Trump, playing up the fact that major Trump donor Timothy Mellon is also the biggest donor to a political action committee supporting the Kennedy campaign.

Mr Trump, meanwhile, has praised Mr Kennedy Jr. In a post on Truth Social he wrote: "He is Crooked Joe Biden's Political Opponent, not mine. I love that he is running!"

At the same time, some Trump supporters have grown concerned he poses a threat and have emphasised Mr Kennedy Jr's views on the environment and other issues in an attempt to paint him as a far-left radical.