To become valid as part of the Constitution, the Twenty-third Amendment needed to be ratified by the legislatures of three-quarters of the states (38, following admission of Alaska and Hawaii to the union in 1959) within seven years from its submission to the states by Congress (June 16, 1967). President Eisenhower, along with both major party candidates in the 1960 presidential election, Vice President Richard Nixon and Senator John F. Kennedy from Massachusetts, endorsed the proposal. Amendment supporters ran an effective ratification campaign, mobilizing persons in almost every state to press for its approval.