I found this interesting article in a random JFK dig.
Instead of posting the article, I'll just post the link (article is long)
On Nov 19, 1963, just 3 days before being assassinated, JFK told his personal Secretary that he was going to remove LBJ as VP on the 1964 ticket. His secretary wrote a book in 1968 and disclosed this
https://www.thedailybeast.com/it-will-not-be-lyndon-why-jfk-wanted-to-drop-lbj-for-reelection