Nov. 22 will mark the 50th anniversary of the John F. Kennedy assassination. Get ready for more of this:

“John F. Kennedy was murdered by a conspiracy involving disgruntled CIA agents, anti-Castro Cubans, and members of the Mafia, all of whom were extremely angry at what they viewed as Kennedy’s appeasement policies toward Communist Cuba and the Soviet Union.”

That’s according to Jesse Ventura in his new book, “They Killed Our President: 63 Reasons to Believe There Was a Conspiracy to Assassinate JFK.” Ventura’s “smoking gun” is a memo written three days after the assassination (and after Jack Ruby shot Lee Harvey Oswald) by Deputy Attorney General Nicholas Katzenbach to Bill Moyers, an aide to newly sworn-in President Lyndon B. Johnson.

“The public must be satisfied that Oswald was the assassin; that he did not have confederates who are still at large; and that the evidence was such that he would have been convicted at trial,” Katzenbach wrote.

Alone, it sounds ominous. But not when viewed in the context of the sentence that precedes it: “It is important that all the facts surrounding President Kennedy’s assassination be made public in a way that will satisfy people in the United States and abroad that all of the facts have been told and that a statement to this effect be made now.”

My hunch is that Katzenbach was already anticipating that, 50 years later, guys like Ventura would seek to prosper by spinning yarns. Katzenbach died in 2012. But Moyers is still with us, and I asked him what he thought of the current use of the memo he was sent 50 years ago. He told me he hasn’t kept up with any of this since leaving the White House, “never even been to the LBJ Library to review my files,” he said by email.

“Some of my old colleagues and I collaborated a few years ago in a protest to the History Channel over a scurrilous documentary about LBJ and the assassination, but that’s been the extent of the attention I’ve given it,” he wrote. “The Warren Commission settled the matter for me, and conspiracy theories of any kind have always seemed a waste of time. I don’t even believe George W. Bush was behind the 9/11 attacks, and as a result am a constant target of those conspiracy theorists.”

Typical was this exchange between us:

MS: You wrote the book “They Killed Our President.” Who are “they”?

JV: No one will ever know, no one will ever know. All I know is, Lee Harvey Oswald didn’t.

Part of Ventura’s explanation is that Oswald had a body double. I kid you not. While he doesn’t know who killed Kennedy, he believes FBI Director J. Edgar Hoover was in on it. Johnson, too. And he impugned the integrity of Arlen Specter, who was, of course, a Warren Commission lawyer who developed what came to be known as the “single-bullet theory.”

Too bad Specter, who died last year, isn’t here to defend himself. He didn’t take JFK conspiracies lightly. I recall how very angry he was about Oliver Stone’s movie “JFK.” Specter thought he’d been defamed by the director and considered filing a lawsuit.

So passionate was Specter for the truth about the Warren Commission that he told me he intended to maintain an active speaking schedule during the 50th anniversary in order to defend his conclusion of many years ago. And I’ll never forget once scheduling a radio interview with Specter back-to-back with pathologist Cyril Wecht, a Warren Commission skeptic.

Wecht went first, and Specter insisted on sitting on hold so he could hear his sparring partner. He then responded to all of Wecht’s assertions. For example, he said: “When Dr. Wecht talks about the direction of the bullet, many people have challenged the direction because the hole in President Kennedy’s shirt was way down, and they said: ‘Well, if the bullet entered there, it had to go up.’ But the issue is not where the hole is on the shirt, but where it is on the body, and President Kennedy’s shirt rode up.”

On the 40th anniversary, Specter told me this:

“I wrote it all down because hardly a week goes by that I’m not asked about it, at high schools and colleges, and I thought the guy who came up with it ought to write it all down because people will be interested in this for a long time.”

About that last statement, there is no debate.

Michael Smerconish writes for The Philadelphia Inquirer. Readers may contact him via www.smerconish.com.