Kennedy would have gotten us out of Vietnam so that would've have plagued Johnson during the primary.
Rubbish; always remember that it was St Kennedy of Brookline's appointees that led LBJ (who was, and this should never be forgotton, a foreign policy ignorant) to escalate the war in Vietnam.
People only think that JFK would have gotten the U.S out of Vietnam because they want to think that he would have done...
My point exactly. Though, as you say yourself, Johnson didn't actively run foreign policy himself. Kennedy may have overruled these appointees. But that is a maybe only.