RFK Jr wasn't campaigning as an anti-vaxxer - until Rogan controversy

Robert F Kennedy Jr has downplayed his anti-vaccine views in his run for the US presidency, but a podcast appearance has put them front and centre once again.

Mr Kennedy, who's seeking the Democratic party nomination for president, is facing controversy after raising his anti-vaccine views on the Joe Rogan podcast.

He appeared on the massively popular series - known for its wide-ranging conversations and a range of guests, including a number with controversial or pseudoscientific views - last Thursday.

Now he's facing pushback for repeating several disproven statements that he's made as head of anti-vaccine charity Children's Health Defense. Among them was the widely debunked idea that vaccines cause autism.

The controversy has focused attention on Mr Kennedy's anti-vaccine views - something he's mostly avoided talking about on the campaign trail.

Peter Hotez is dean of the National School of Tropical Medicine and a professor at Baylor College of Medicine. He's also been a guest on Mr Rogan's podcast, but on Twitter called the interview with Mr Kennedy "just awful".

The doctor says that prompted a wave of abuse. It also spawned offers by Mr Rogan and others to donate large sums of money to charity if Dr Hotez debates Mr Kennedy about vaccines.

Mr Kennedy tweeted: "Let's finally have the respectful, congenial, informative debate that the American people deserve."

Dr Hotez has so far turned down the offers. In interviews he has said he's willing to appear again on Mr Rogan's show but that he does not want to argue with Mr Kennedy.

Mr Kennedy belongs to America's most famous political family, though he made his own name through legal work for environmental causes.

For years he's also been a major figure in the anti-vaccine movement. In 2005 he published an article in Rolling Stone and Salon, claiming a link between vaccines and autism. It was later withdrawn by both news organisations after criticism and fact-checking.

His profile has been on the rise along with the rest of the anti-vaccine movement, which seized on the Covid pandemic to advance its agenda.

In 2021, Mr Kennedy was named as one of the main spreaders of anti-vaccine falsehoods - one of a so-called "disinformation dozen" - in a CCDH report.

Children's Health Defense has sued the BBC and other organisations, alleging that violations of US anti-trust laws resulted in censorship of the group's views

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Despite the heightened profile for his foundation, Mr Kennedy has not put his vaccine views at the centre of his campaign for president.

During a nearly two-hour speech to kick off his campaign in April, he criticised Covid lockdowns, government spending, corporate power and Donald Trump. But he only briefly mentioned vaccines and didn't dwell on his anti-vaccination activism.

Likewise, his campaign web site highlights his positions on the environment and civil liberties, rather than the issue that supercharged his popularity on social media and prompted several other Kennedy family members to disavow his campaign.

One simple explanation for the omission is that Mr Kennedy's stances on vaccines are not very popular in his own political party.

Imran Ahmed, chief executive of the Center for Countering Digital Hate, a non-profit that works against disinformation, told the BBC that "being an anti-vaxxer is still a minority pursuit in the United States".

"So he's sticking to a more general anti-establishment schtick," he says. "He's working really hard to keep people from knowing he's a hardcore anti-vaxxer."

Mark Schmitt, a research director at New America, a left-leaning think tank, said Democratic voters "overwhelming say" they are in favour of vaccines, including the Covid jab.

Mr Schmitt notes that the picture among Republicans is more mixed, although generally more favourable than not. He credits name recognition with Mr Kennedy's popularity among Democrats.

Mr Kennedy, the 69-year-old son of assassinated Senator Robert F Kennedy, is challenging incumbent Joe Biden. While his campaign is viewed as a long shot, several recent opinion polls suggest he has the support of around 20% of Democratic voters.

"He's saying, I'm someone fresh but recognisable, I'm not from the establishment but you know my family," says Mr Ahmed.

The BBC contacted Spotify, which hosts the podcast, and Mr Kennedy for comment.