No. He didn't. It doesn't add up. A man who kills to get the White House doesn't refuse to run for reelection due to popularity concerns. Also, Johnson was concerned about his health having been told by an actuary that he wouldn't likely live past 64. He died at age 64. Also, RFK announced his candidacy middle of March, Johnson said he wouldn't run at the end of March, and RFK was shot in June. Why kill him after you intend not to run? I get that what actually happened is boring by comparison to a conspiracy theory, but that's how life is. It's often more plain than we want it to be. All it takes is a crazy guy with a rifle to kill a president. That's it.