Researching the Kennedys and hating the President has me thinking a lot about primary challenges to incumbent presidents. After FDR fundamentally changed the American presidency by running for president until he died, the 22nd amendment was added to the constitution, limiting each subsequent president to two terms. This means that most presidents, once elected, do try to run for another term. Of course, presidents usually face challengers from the opposite party, but do they ever face a primary challenger?

I mentioned the Kennedys earlier, because one of the more famous primary challenges was Robert F. Kennedy, who ran for the Democratic nomination in 1968. In 1968, LBJ was the incumbent candidate. He had taken over after JFK was assassinated in 1963, and was elected in his own right in 1964. But come 1968, LBJ was very unpopular with anti-war segments of the party. After anti-war candidate Eugene McCarthy won a primary in New Hampshire, and RFK entered the race, LBJ sensed the changing winds and withdrew, choosing not to run again.

Of course, RFK was later assassinated, and McCarthy lost the primary to Hubert Humphrey, LBJ's Vice President, who then lost the general election to Nixon.