Sharjah24 - AFP: During a campaign stop in Philadelphia on Thursday, the illustrious Kennedy family will support US President Joe Biden, highlighting the electoral threat posed by independent candidate Robert F. Kennedy Jr. and the family's black sheep.

Fifteen members of the politically influential family will back Biden amid fears that a strong showing by conspiracy theorist and vaccine-skeptic "RFK Jr" could tilt the victory to Donald Trump in November's US presidential vote.

The environmental lawyer is the son of Robert F. Kennedy Sr, who served as attorney general under assassinated president John F. Kennedy, and was himself shot dead in 1968 during his own presidential bid.

The candidate's sister Kerry Kennedy is set to introduce Biden at the event, which will be the crowning moment of a three-day swing through the crucial battleground state of Pennsylvania.

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

"I can only imagine how Donald Trump's outrageous lies and behavior would have horrified my father," the remarks continued.

"A vote for Joe Biden is a vote to save our democracy and our decency."

Biden will also speak at a grassroots event, introduced by RFK Jr's nephew, Joe Kennedy III, who serves as Biden's special envoy to Northern Ireland for economic affairs, before family members go out doorknocking.

Robert F. Kennedy Jr said he respected their decision to back his electoral rival.

"I hear some of my family will be endorsing President Biden today. I am pleased they are politically active -- it’s a family tradition," he said on X.

"We are divided in our opinions but united in our love for each other."

- Storied surname -
The endorsement will not be the first show of force in support of Biden by America's most mythologized political family.

Dozens of Kennedys posed with President Biden in a photo in the Rose Garden of the White House to mark Saint Patrick's Day in March as they celebrated their shared Irish heritage.

And Biden has long channeled the Kennedys in his own political narrative.

The 81-year-old has a bronze bust of Robert F. Kennedy Sr in the Oval Office that can be seen behind him in photos whenever he meets foreign dignitaries at the White House.

Biographies of Biden say he had long aimed to emulate the soaring rhetoric of John F. Kennedy, the young Democratic president shot down in his prime in 1963.

Armed with the storied surname, Robert F. Kennedy's wildcard shot for the presidency risks being a spoiler for Biden's hopes of a second term in the White House.

Kennedy, a vaccine skeptic who has spread misinformation downplaying the 2021 insurrection at the US Capitol, is boasting double-digit support in polls with the election less than seven months away.

Democrats have learned to fear long-shot outsiders after George W. Bush and Trump won tight elections in 2000 and 2016, buoyed by Green Party candidates siphoning votes from Al Gore and Hillary Clinton.

Kennedy, 70, started his White House bid as a Democrat, but exited the primary after complaining of bullying tactics by Biden allies seeking to keep him out of contention.