Who will actually vote for Robert F Kennedy Jr as an independent candidate?

Robert F Kennedy Jr - the anti-vaccination activist, environmental lawyer and member of America's most famous political family - is expected to announce on Monday that he's running for president as an independent candidate.

Although his chances of capturing the White House in 2024 are slim to none, he could potentially impact a close race. So who are his supporters - and might he take more votes from the Republican or Democratic nominee?

"If it becomes a choice between Trump and Kennedy, that's a really tough question," says Sherri Guoan. "In a perfect world, I would love for them to run together."

Mrs Guoan and her husband Brandon drove more than an hour from the Detroit area to see Mr Kennedy in Michigan's state capital on Saturday.

Mr Guoan calls himself an "old school Democrat, a Kennedy Democrat." But the couple both voted for Donald Trump in 2020.

"Trump is very controversial and I think the country could use a fresh start," she says, but there's no way she'll vote for Joe Biden, whom she calls "the worst president this country has ever had."

The BBC spoke to dozens of voters in an eclectic crowd of a few hundred in Lansing. They offered some clues into how a Kennedy campaign might alter the overall race - and in what direction.

Standing just a few feet away from the Guaons is retired autoworker and proud union member Alex Hernandez. A Democrat who voted for Mr Biden, he recalls his parents taking him to see a speech by Mr Kennedy's father in 1968.

"He has the name and he has the heritage," he says of the younger Kennedy. "I wanted to come down here and hear what he has to say."

Robert F Kennedy Jr is part of a Democratic political dynasty. He counts a president and senator among his uncles, and in 1968 his father was assassinated while running for the party's presidential nomination.

Mr Kennedy began his own quest for the White House earlier this year by entering the party's nomination process. He never mounted a real challenge to President Joe Biden, however, and at a rally in Philadelphia on Monday he is expected to declare he is running as an independent candidate instead.

The switch reflects how the policies and priorities of Mr Kennedy and the modern Democratic Party have diverged. His deep scepticism about vaccines and the push to support Ukraine, for example, are out of step with most Democratic politicians.

Mr Kennedy spent most of his career as an environmental lawyer but has been more recently known for spreading doubt and falsehoods about vaccinations through his foundation, Children's Health Defense, which got huge boosts in funding and publicity during the Covid pandemic.

His signature issue resonates more with grassroots Republican voters than with Democrats. And in a recent podcast interview, Mr Kennedy said: "I take more votes from President Trump than I do from President Biden."

A recent poll funded by a political action committee backing the Kennedy campaign indicated that in a three-way race, Mr Kennedy Jr would siphon off slightly more support from Donald Trump than from Joe Biden. However, another survey, conducted by Ipsos and Reuters, showed the opposite.

In his stump speech in Michigan on Saturday, Kennedy emphasised his environmental credentials, a populist economic message, and the history of his political family - only mentioning vaccines very briefly.

"People feel that the system is disintegrating," he told the crowd. "Not just economically, but mental health and physical health, and all these communities are being torn apart in all these different ways… A lot of them are living paycheque to paycheque, at the edge of desperation."

Many voters said they had voted for Mr Trump and preferred his policies, if not his personality. But there were no shortage of self-declared Democrats or people who said they would refuse to vote for either of the major parties.

"If I didn't have an option of Kennedy, I would probably just write him in," says Matthew Ruggles. Two of his friends standing nearby agree. "There's no point in voting for either of those [major] parties."

"A third party candidate can attract people who aren't interested in the other candidates - maybe they did vote in the past but they felt overlooked," says Melissa Smith, author of Third Parties, Outsiders, and Renegades: Modern Challenges to the Two-Party System in Presidential Elections.

When it comes to the raw vote numbers, Ms Smith says, the true impact of an independent candidate can be hard to gauge, even after an election.

In 2020, the closest state, Georgia, was decided by just more than 11,000 votes. At the same time, more than 60,000 Georgians voted for the Libertarian Party ticket headed by Jo Jorgenson. The Libertarian vote was also greater than Joe Biden's margin of victory in the crucial states of Wisconsin and Arizona.

But whether in the absence of a third party those voters would have voted for Mr Trump, Mr Biden or not at all is a nearly impossible question to answer.

And Ms Smith says that simple dissatisfaction with the major parties is not enough to push most voters to independent and third party candidates.

Mr Kennedy also faces a different challenge to previous would-be disruptors of the two-party system. Because Mr Trump has already claimed the mantle of anti-establishment outsider, and reshaped the Republican Party in his populist image, there is simply less political terrain available to exploit.

That is why Mr Kennedy's stance on vaccines, which for years has run contrary to the scientific mainstream, may be one issue where he stands out from the other candidates - even if he is currently avoiding focusing on it.

Mr Kennedy, Ms Smith says, "trades in conspiracy theories and that's what's going to attract some people" - even though Mr Trump has himself spread falsehoods about widespread election fraud.

For many in the crowd on Saturday, Mr Kennedy's views on vaccines were part of his appeal - a feature, rather than a bug. Several repeated debunked theories about a connection between childhood vaccines and autism, while several more mentioned their opposition to vaccine mandates, whether by the government or private companies.

"We're not saying vaccines aren't good. We're not saying they're bad. We just want to ask about them," says student Jacob Kostecke, who was wearing a Kennedy t-shirt and says he's planning on a career in the medical field.

"He's just trying to keep an open mind and just bring us together, where I feel like everything's just so divided and so political right now."

More than a year away from the actual presidential election in November 2024, it is impossible to know if the Kennedy campaign will catch fire or remain a fringe movement. But Jacob says if Mr Kennedy was not on the ballot, he would vote for Mr Trump.