Mr. Corsi, who has worked with the conspiracy theorist Alex Jones on his Infowars operation, has dealt with Mr. Stone on and off for years. Mr. Corsi was also one of the people whom President Trump, before he was a candidate, contacted for information about former President Barack Obama’s birth certificate in pressing the false claim that Mr. Obama was not born in the United States.

Mr. Corsi’s name came up when federal agents stopped and detained a professor and author, Ted Malloch, at a Boston airport last March. Mr. Malloch told NBC at the time that, among other questions, federal investigators asked him about Mr. Stone, whom he had met a handful of times, about WikiLeaks and about Mr. Corsi, who had helped edit one of his books.

In testimony before the House Intelligence Committee last year, Mr. Stone, who had predicted in a 2016 tweet that Mrs. Clinton’s campaign chairman, John Podesta, would face his “time in the barrel,” said he based his tweet off research given to him by Mr. Corsi, whom he identified as an investigative journalist. He said that Mr. Corsi’s research was drawn from public information related to Mr. Podesta’s brother, the lobbyist Tony Podesta.

John Podesta’s private email account was hacked in 2016 and some of the content was posted by WikiLeaks in October 2016, just as Mr. Trump was facing questions about the “Access Hollywood” tape on which he was recorded in 2005 boasting about grabbing women by their genitals.