RFK Jr: How anti-vaccine misinformation has shaped his 'truth-teller' candidacy

America faces an election rematch in November that few voters are motivated by. As a result, independent candidates could have a bigger impact on this year's result than they have in decades, and none is making bigger waves than Robert F Kennedy Jr.

His supporters see him as a courageous truth-teller, battling nefarious corporate powers. Yet the vaccine sceptic has a history of straying from the truth and spreading health information scientists say is false. Rachel Schraer investigates these two very different images.

About 20 years ago, Professor Paul Offit received a phone call.

"Robert F Kennedy Junior called me and he said that he needed my help," says the scientist, whose vaccine against rotavirus is estimated to save some two thousand lives a day in the developing world.

Mr Kennedy, a member of the famous political dynasty and nephew of former president John F Kennedy, told Prof Offit he was looking for information. He wanted to reassure parents who were worried about the effects of a mercury-based preservative called thimerosal, found in some vaccines.

Prof Offit confesses he was excited to be able to talk a Kennedy through the studies, which showed children exposed to thimerosal (not found in most US vaccines anyway since 2001) were no worse off than those who hadn't had exposure.

But a year or so later, Mr Kennedy wrote an article published in Rolling Stone magazine which repeated baseless claims that thimerosal was causing health problems. It also wrongly claimed the vaccine that Prof Offit was working on at the time contained this preservative, suggesting this had driven him to misrepresent the risks. The article was later retracted due to a large number of inaccuracies.

Despite these wrong claims, Mr Kennedy - now a presidential candidate - appeared on Joe Rogan's podcast last summer repeating his version of the story.

We contacted Mr Kennedy's team but they did not comment on this specific allegation.

"I think he's remarkably dishonest," Prof Offit says.

You can listen to Trending: "The anti-vax candidate?" on BBC Sounds.

And yet, honesty is one of the main reasons RFK Jr's supporters from across the political spectrum have told the BBC they want him to be the next US president.

A January Gallup poll suggested he was the only candidate with a more than 50% favourability rating among the public. That may not mean anything for how people will actually vote, though, with the two major party candidates still expected to draw the vast majority of votes.

The worry for both Democrats and Republicans, however, is that RFK Jr might siphon off votes in November that might have otherwise gone to their candidates - set to be Joe Biden and Donald Trump.

Jay Scott, one supporter, described him as a "courageous truth-teller".

Another, Michigan-based independent voter Bryce Lipscombe told me: "I just trust the man who has sued a bunch of these government agencies and won, who has actually proven that corruption exists."

Many supporters from across the political spectrum said they liked the fact Mr Kennedy was promising to tackle the influence of big business on government, including pharmaceutical companies and the oil and gas industry,

They said they found his policies on immigration and drug legalisation to be sensible. And they pointed to his record as an environmental lawyer of suing companies that pollute, with some notable successes including cleaning up the Hudson River in New York.

Mr Kennedy appeared to speak especially to people who were unhappy with - or suspicious of - the US government and the rest of the world's response to the Covid pandemic.

Mr Kennedy's supporters point to genuine failings by public institutions on issues from the opioid crisis to the Iraq war as reasons they've lost trust in the two main parties.

But this doesn't change the fact there are also countless examples of Mr Kennedy spreading conspiracy theories, making false or misleading statements, and sticking by his positions regardless of the evidence presented to the contrary.

"Whenever presented with copious evidence and scientific studies that vaccines do not cause autism… or whatever health condition he attributes to them, it is never enough," said Dr David Gorski, professor of surgery at Wayne State University and managing editor of the site Science Based Medicine. "He always moves the goalposts, demanding still more evidence."

When contacted for comment, Mr Kennedy's team maintained that: "Proper safety studies have never been conducted on vaccines: long-term, all-cause mortality studies comparing fully-vaccinated children to never-vaccinated children.

Many Kennedy supporters echo this argument but Dr Gorski says it "just plain not true".

He explains that for decades countless groups of independent scientists have looked at the effect of vaccines on a huge range of specific health outcomes and found the benefits far outweigh any risks.

For Prof Offit, this tactic represents what he sees as the impossibility of debating him.

"What do you do with people like Robert Kennedy Junior?" he asks. "When he raises the question: 'Could this vaccine do harm?', and then excellent studies are done showing that it doesn't. And he just refuses to believe them, because he just claims conspiracy at every turn."

But the lack of people willing to debate Mr Kennedy has been held up as just another example - including the past removal of some of his social media accounts - of him being silenced and censored.

This "censorship" is part of the reason Mr Kennedy says he is running for president in the first place.

He was also part of a legal case against the BBC and other news media organisations claiming they and social media platforms colluded to censor him and others so they couldn't compete with them.

For New York magazine correspondent, Olivia Nuzzi, who has interviewed Mr Kennedy and followed his campaign, some of his supporters' deep mistrust of mainstream institutions, from scientists to the media, presents an "impossible" problem for those seeking to fact-check his claims. "It's like two different universes of facts," she says.

Those who distrust powerful institutions are "willing to give someone the benefit of the doubt who they perceive to be righteously challenging that power," she says, and are, "not interested in arguments from people that they perceive to be doing the bidding of those institutions".

Many of RFK Jr's supporters are impatient with discussion of his stance on vaccines. Some think it's an attempt by the media to smear him. For others it is simply less important than other issues like the border, surveillance and the economy, including tackling the influence of powerful corporations.

But it seems crucial in the question of his relationship to the truth.

"If you're going to speak truth to power," Prof Offit says, "You should at least tell the truth."