Robert Kennedy, Jr., 2024 Presidential hopeful, meets with people at the New Hampshire State House Visitor Center, in Concord, New Hampshire, on June 1, 2023. (Photo by Joseph Prezioso / AFP) (Photo by JOSEPH PREZIOSO/AFP via Getty Images)

Robert Kennedy, Jr., 2024 Presidential hopeful, meets with people at the New Hampshire State House Visitor Center, in Concord, New Hampshire, on June 1, 2023. (Photo by Joseph Prezioso / AFP) (Photo by JOSEPH PREZIOSO/AFP via Getty Images) / AFP via Getty Images

Robert F. Kennedy Jr. made headlines this week when he confirmed a report that he once had a parasitic worm in his brain. But President Joe Biden and former president Donald Trump were already paying attention to the independent candidate.

Biden has touted endorsements from more than a dozen Kennedy family members, and Trump attacked Kennedy Jr. as a "Democrat Plant" on social media. That attention is just one sign that his candidacy could have a real impact on this year's election.

NPR's Scott Detrow speaks with presidential historian Barbara Perry and Bernard Tamas, an expert on U.S. third parties, on the historic affect of third party candidates.

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