“They were betting not only the civil rights movement but their own careers. And they knew that Hoover was out to ruin King,” said Robert Kennedy Jr., referring to J. Edgar Hoover, the FBI director at the time.

He argued that the Kennedy administration had a legitimate reason to go along with Hoover’s determination to surveil King. The FBI director saw King as a dangerous radical with Communists in his inner circle.

“There was good reason for them doing that at the time,” Kennedy said, “because J. Edgar Hoover was out to destroy Martin Luther King and the civil rights movement and Hoover said to them that Martin Luther King’s chief was a communist.

“My father gave permission to Hoover to wiretap them so he could prove that his suspicions about King were either right or wrong,” he continued. “I think, politically, they had to do it.”

By defending his family’s participation in what is widely considered a shameful episode in presidential history, Kennedy may complicate his efforts to present himself to the electorate as a political truth teller who stands up for marginalized constituencies.

The attorney and anti-vaccine activist has attempted in his campaign to reach out to Black voters and other racial minorities that typically lean toward the Democratic Party. His renowned lineage has so far seemed to be an asset in that effort.

But Kennedy’s relationship with his family is complicated and strained, with some of his relatives speaking out against his candidacy and his fringe views that in many cases appeal to the right.

On Sunday, Kennedy was on the campaign trail in Atlanta with Angela Stanton-King, a former Republican congressional candidate and Donald Trump supporter who now works for Kennedy’s campaign.

Declassified government records revealed that the FBI engaged in a sustained campaign of surveillance and harassment targeting the Civil Rights movement, to a far greater extent even than was publicly known at the time. Most notoriously, the FBI sent King a letter suggesting that the Civil Rights leader should kill himself.

Betty Medsger’s 2014 book “The Burglary: The Discovery of J. Edgar Hoover’s Secret FBI” characterized the FBI’s campaign against King as a “yearslong multifaceted operation designed to destroy King.”

Medsger added: “The plot involved office break-ins, use of informers, mail opening, wiretapping, and bugging of King’s office, home and hotel rooms.”

Robert Kennedy Jr. said on Sunday that his father and uncle would have been fully aware of Hoover’s hostility to civil rights organizations: the FBI director was “a racist,” Kennedy said, and “left no doubt where he stood on those issues.”

He claimed, however, that his uncle as president would have fired Hoover in a second term, had he not been assassinated in the fall of 1963.

Kennedy also said he believed that President Kennedy had alerted King to the eavesdropping in a private conversation.

David Cohen contributed to this report.