4. George H.W. Bush
We've already covered the obvious gains that Lyndon Johnson would have acquired with Jack Kennedy out of the way, but Bush 41? Really? Going back to the popular CIA theory, Bush served as Director of the CIA from 1976 until he was elected Vice President in 1980. The theory is that Bush was previously a member of the CIA and personally orchestrated the alleged hit on Kennedy due to his misgivings regarding the agency's murderous actions against Castro. There is photographic evidence that one of Bush's Skull & Bones brothers was Mac Wallace, who was allegedly a hit man for President Johnson, which fuels the speculation that Bush would personally vet Wallace to carry out the hit that would make his friend the next President. Bush also allegedly had personal connections to the Mafia, and is even suspected of ordering the shooting down of JFK Jr.'s plane! Might wanna cut down on those murderous tendencies, Mr. President. It wouldn't be prudent.