Nixon didn't have anything to do with Kennedy's murder.What was his motive?  He wasn't the VP, a heartbeat from the Presidency, like your buddy Johnson was. The assassination united the country behind Johnson, not Nixon. That would be expected and as good a motive for murder as any detective could find.  And who chose to run against Johnson in 1964? Another good buddy of yours, Barry Goldwater. He got swamped in '64. 
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So Nixon has Kennedy done in so he can wait 8 years until Johnson finishes 2 terms, hoping to make a comeback in '72?  Nope, your all wet on that one.  Nixon had no great love for the Kennedy's and that is the craziest, most  debunked conspiracy theory there's been. Trump is no different than most of us, he likes a good conspiracy theory, but its mostly entertainment.  Like playing a game of  "Clue"  
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Communists killed Kennedy. The obvious assumption is usually the most logical. Oswald was probably promised Cuban or Russian citizenship for his 'comradeship'  They lied