Ms. Nuzzi told her editors about the relationship that had turned personal, the outlet said. A representative for Mr. Kennedy said the pair had met only once.

One of America’s most acclaimed magazine writers, Olivia Nuzzi of New York magazine, has been placed on leave while a “third-party review” is conducted after Nuzzi disclosed that she “had engaged in a personal relationship with a former subject relevant to the 2024 campaign while she was reporting on the campaign.