You sure are working hard to claim that JFK couldn’t pass his bills if reelected, that only his veep could.
LBJ was Majority Leader of the Senate for a long time and was known for his ability to strong arm Senators and House Members to get his way.
He was a wheeler dealer.
Also remember that LBJ was also a contender for the 1960 Democrat nomination. Also Johnson was not accustomed to losing.
Johnson would not be happy being second banana to Kennedy.
If Johnson had not been successful in engineering Kennedy’s assassination I would have expected him to run against Kennedy for the 1964 nomination.
I am not claiming that Kennedy could not pass bills.
My supposition is that Johnson would be better at it and that if Johnson applied his famous ‘Treatment’ any bill had a much better chance of passing.