What did Lyndon B. Johnson Think About the JFK Assassination?

While it is well documented the views of Earl Warren and other members of the Warren Commission surrounding the assassination of John F. Kennedy, what did Kennedy's vice-president and successor, LBJ, believe about the Kennedy assassination? From the get-go, Johnson was utterly obsessed with the possibility of a foreign conspiracy involving the Soviet Union and/or Cuba as this November 29th, 1963 telephone conversation between Johnson and Senator Richard Russell Jr. demonstrates:

And, indeed, it would be those potential international connections of Oswald that would lead to Johnson never discounting the possibility of an international conspiracy, even after the release of the Warren Commission Report and the Clark Panel:

It has been claimed that Johnson positively believed in a conspiracy, specifically regarding Cuba and Fidel Castro. In a July 1973 article published in The Atlantic, LBJ speechwriter Leo Janos wrote comments allegedly made by LBJ after his administration, during dinner on the third floor of the LBJ Library. Here is the quote:

"During coffee, the talk turned to President Kennedy, and Johnson expressed his belief that the assassination in Dallas had been part of a conspiracy. "I never believed that Oswald acted alone, although I can accept that he pulled the trigger." Johnson said that when he had taken office he found that "we had been operating a damned Murder Inc. in the Caribbean." A year or so before Kennedy's death a CIA-backed assassination team had been picked up in Havana. Johnson speculated that Dallas had been a retaliation for this thwarted attempt, although he couldn't prove it. "After the Warren Commission reported in, I asked Ramsey Clark [then Attorney General] to quietly look into the whole thing. Only two weeks later he reported back that he couldn't find anything new." Disgust tinged Johnson's voice as the conversation came to an end. "I thought I had appointed Tom Clark's son—I was wrong.""

Did Johnson actually say such things? Perhaps, it certainly fits his character. Regardless of what personally believed, however, he was self-honest enough to admit that he "couldn't prove it".

Sources:

“You’re Goddamn Sure Going to Serve” | The LBJ Telephone Tapes (lbjtapes.org)

LBJ Speaks on a conspiracy in JFK Murder (youtube.com)

The Last Days of the President - The Atlantic