Roger Stone is writing a book based on his conspiracy theory that the Clintons murdered John F. Kennedy Jr. Stone is an longtime ally and friend of Donald Trump, who has previously used the discredited operative's research in attacks against the Clintons.

Stone worked as a top political aide to Trump's presidential campaign before exiting in August. Stone is a notorious “dirty trickster” who formed the anti-Hillary Clinton group C.U.N.T. in 2008 and has spent much of the 2016 cycle pushing smears about the Clintons. He has a history of using racist and sexist attacks against media figures, and was recently banned by CNN and MSNBC. He currently heads the pro-Trump super PAC Committee to Restore America's Greatness and is a frequent Trump supporter in the media. Stone has been under heavy criticism recently because of his stated plan to “disclose the hotels and the room numbers of those delegates who are directly involved in” allegedly stealing the nomination from Trump at the Republican convention.

Stone last month appeared on the internet radio show of fringe conspiracy theorist James Fetzer, who believes the Holocaust, Sandy Hook Elementary School shooting, and 9/11 attacks were faked. During a brief aside, Stone mentioned he was writing books about Sen. Cory Booker (D-NJ) and the alleged murder of John F. Kennedy Jr. “by the Clintons”:

ROGER STONE: I have coming up next year a book which I make the case that John F. Kennedy Jr. was murdered. And he was murdered by the Clintons because he was in the way. Now I have extraordinary new evidence that nobody else has seen.

Fetzer later told Stone that JFK Jr. was assassinated and offered to give Stone “leads” proving it. Stone responded, “That’s great to know, Jim. As you know, there’s really nobody in the researcher community that I respect more than you.”

JFK Jr. died after a plane he was piloting crashed in July 1999. The National Transportation Safety Board found that his plane crash was an accident and the probable cause was the “pilot's failure to maintain control of the airplane during a descent over water at night, which was a result of spatial disorientation. Factors in the accident were haze and the dark night."

Trump has sourced some of his attacks against the Clintons to Stone. During a January 5 appearance on Fox News' Hannity, host Sean Hannity asked Trump about calling Hillary Clinton an “enabler” of “one of the great woman abusers of all time,” President Bill Clinton. Trump responded by referencing Stone’s book The Clintons’ War on Women, stating that “a major book's been written about it, and it's a book that's a very well respected book. And it was not a pretty picture, what she did.” Stone co-authored the book with fringe conspiracy theorist Robert Morrow.

The New York Times noted in December that Trump “appears to be taking a page from the playbook of his former political adviser Roger Stone” with his attacks on the Clintons.

In October, Trump tweeted a link to Stone’s The Clintons’ War on Women book and commented, “The latest book on Hillary—Wow, a really tough one!” Stone has said that he and Trump talk “From time to time. … We're still talking politics. I'm involved with a PAC that is specifically doing one narrow thing, which is collecting evidence of voter fraud.”

Stone previously wrote that the Clintons did not murder JFK Jr. In The Clintons’ War on Women, Stone argued the Clintons are “plausibly responsible” for the deaths of roughly 40 people, but added, “They are not responsible for the death of John F. Kennedy, Jr., as some researchers have claimed”:

There is no question that some Clinton critics are excessive. There are widespread claims that the Clintons are responsible for the death of as many as eighty-three people whose knowledge stood in the way of their political ascent. Based on our investigation, the Clintons are only plausibly responsible for the deaths of half the people on this list. They are not responsible for the death of John F. Kennedy, Jr., as some researchers have claimed, though the number of individuals who are both knowledgeable of and pivotal to the Clintons’ grasp for power who die in plane crashes defies mathematical odds.

During a March 9 appearance on the internet-based program Caravan to Midnight, Stone said JFK Jr. was murdered and “almost everything you’ve been told about his plane crash and death is false or embellished or cooked.”

Last year, Stone tweeted that “The MURDER of JFK, Jr. will be the subject of my next book #Clintons #guilty” and “JFK Jr was planning on running for NY Senate seat @HillaryClinton wanted. Poor bastard.”

@MichaelDelauzon The MURDER of JFK, Jr. will be the subject of my next book#Clintons #guilty — Roger Stone (@RogerJStoneJr) October 20, 2015