More: Over Mr. Kennedy's speaker phone, Mr. Trump, the Republican nominee, can first be heard describing scientifically baseless concerns about vaccinations " an issue Mr. Kennedy is closely associated with " expressing disbelief at the volume of vaccinations given to infants.

"I want to do small doses," Mr. Trump said, before observing that the practice of giving multiple vaccinations at once means the shot "looks like it's meant for a horse, not uh, you know, a 10-pound or 20-pound baby."

Mr. Kennedy and the organization he co-founded, Children's Health Defense, have for years promoted claims about the health risks of childhood vaccines that have repeatedly been refuted by studies.

"And then you see the baby all of a sudden starting to change radically, I've seen it too many times," Mr. Trump said. "And then you hear that it doesn't have an impact, right? But you and I talked about that all the time."

Then Mr. Trump pivoted to an apparent effort to win his support: "I would love you to do something. And I think it'll be so good for you and so big for you. And we're going to win."

Mr. Kennedy, standing while wearing a shirt and tie, says "Yeah," barely audibly. Throughout the video, Mr. Kennedy says little else.

Mr. Trump also briefly described his recent call with President Biden and said he had asked about the near miss of the bullet in Pennsylvania. "It was very nice, actually," Mr. Trump said. "He called me, and he said, How did you choose to move to the right?'"

Mr. Trump marveled that he had been shot by an AR-15-type weapon, the sort of military-style rifle Mr. Biden wants to ban " "pretty tough guns, right?"

Of the wound to his ear, Mr. Trump said: "It felt like the world's largest mosquito."