EXPOSED! Former Presidential aide says he has bombshell new evidence revealing America’s greatest coverup claiming that VP Lyndon Johnson was behind the assassination of President JOHN F. KENNEDY.

President John F. Kennedy’s world-shattering assassination while riding in a Dallas motorcade was masterminded by the power- crazed man who took his place in the White House – then Vice President Lyndon Johnson!

And Jack Ruby, the mob-connected nightclub owner who shot to death Kennedy’s assassin Lee Harvey Oswald, silencing him before he could be fully grilled by lawmen, had close ties to Johnson and future President Richard Nixon!

Those are the bombshell charges dropped in a blockbuster new book coming out on the eve of the 50th anniversary of JFK’s death by Roger Stone. The author previously  worked on the Committee to Re-Elect Nixon in 1972 and then served in the Office of Economic Opportunity during Nixon’s scandal ridden second administration.

“If Roger Stone is right – this will change American history forever,” says a long-time Washington insider.

“It changes everything – I mean everything. Everything we have ever believed is about to change.  The whole Kennedy assassination has just blown up in front of our eyes. Lyndon Johnson has just blown up in front of our eyes and so did Richard Nixon.”

According to a source close to Stone’s upcoming book, “The Man Who Killed Kennedy” , “President Johnson…was the driving force behind a conspiracy to murder President John F. Kennedy on November 22, 1963.

“Lyndon Baines Johnson was a man of great ambition and enormous greed. Johnson would use power from his personal connections in Texas and from the underworld and from the government to escape an untimely end in politics and to seize even greater power.”

The claim by Stone, 61, and his co-author Mike Colapietro, an investigative journalist, was previously supported by JFK’s widow Jackie. “She was convinced that it was her husband’s successor who was the mastermind behind the plot to murder JFK,” says a source.

Jackie thought it a convenient coincidence that the murder, while she and JFK were  riding in an open motorcade through Dallas’ Dealy Plaza, took place in Texas, Johnson’s home state, where he’d been a longtime congressman and had powerful connections high and low.

Her suspicions were also fueled by Oswald’s shocking killing – just two days after the assassination — while police were transferring him and before he could reveal anything about the tragic event. She also thought it a strange coincidence that shooter Ruby “was a Texas good ol’ boy,” adds the source.

According to Stone’s book, streeting Nov. 6, Ruby, Johnson and Nixon had a  relationship going back 16 years before Kennedy’s killing.

When Ruby moved from Chicago to Dallas in 1947, he was soon hired by Nixon, then serving along with Johnson in the U.S. House of Representatives.

Stone told the UK Daily Mail he has newly released documents showing that “Nixon knew Jack Ruby, hired him on the House payroll in 1947 at the request of…Lyndon Johnson.”

Stone also accuses Johnson and Texas Gov. John Connally, who was wounded in the assassination, of setting up the motorcade route. “LBJ and Gov. Connally micromanaged JFK’s Dallas schedule and demanded the route through Dealy Plaza where the motorcade came to a full stop and LBJ had JFK killed,” Stone said.

Stone blames Johnson’s insatiable greed and thirst for power. But Jackie believed Johnson and his Texas cronies “despised the Kennedys” and were jealous of the Kennedys who were considered “America’s aristocrats,” says the source.

While JFK and Johnson were both Democrats and running mates, they were also bitter rivals. “JFK and Johnson hated each other to the depths of their being,” says the source.

The Warren Commission later concluded that Oswald was the lone assassin – a ruling  that has been controversial ever since.

But Jackie “became convinced that the then-Vice President, along with businessmen in the South had orchestrated the Dallas shooting” and Oswald was “merely part of a much bigger conspiracy,” notes a source.

Johnson later died of a heart attack in January 1973 while Nixon suffered a fatal stroke in April 1994. Jackie died of cancer in May 1994.

Meanwhile, Stone claims he has exhaustive research to support the devastating findings in his book.

The Washington insider said, “It’s the worst political scandal imaginable. And to think it’s been covered up all these years.”