In New Jersey, incumbent United States Senators have rarely faced competitive primary challenges, and the only incumbent Senator to lose a primary was Clifford Case, a four-term Republican who lost 50.7%-49.3% to conservative Jeffrey Bell, a former speechwriter for Ronald Reagan’s 1976 presidential campaign. Case had faced primary challenges from the right before: Robert Morris, who had been Chief Counsel for Senate Internal Security Subcommittee headed by Joseph McCarthy, won 33% in 1960; and James Walter Ralph, a Bergen County physician, received 30% in 1972.
In 1970, incumbent Harrison Williams faced a Democratic primary challenge from Frank Guarini, then a State Senator from Hudson County. Williams won 66%-34%; eight years later, Guarini was elected to Congress.
One of the fiercest primaries in state history was in 1924, when Republican National Committeeman Hamilton Kean challenged Walter Edge, a former Governor who was completing his first term in the Senate. Edge won, 57%-43%, and Kean went on to win an open seat four years later.