Twenty-second Amendment to the United States Constitution
Since coming into force in 1951, the amendment has applied to six presidents who have been elected twice: Dwight D. Eisenhower, Richard Nixon, Ronald Reagan, Bill Clinton, George W. Bush, and Barack Obama. It has also applied to two who entered office intra-term due to their predecessor's death or resignation: Lyndon B. Johnson and Gerald Ford. Johnson became president in November 1963, following the assassination of John F. Kennedy, served out the final of Kennedy's term, and was elected to a full four-year term in 1964. Four years later, he briefly ran for a second full term, but withdrew from the race during the party primaries. Had Johnson served a second full term – through January 20, 1973 – the total length of his presidency would have been ; as it happened, Johnson died two days after this date. Gerald Ford, who became president in August 1974 following the resignation of Richard Nixon, served the final of Nixon's term, and attempted to win a full four-year term in 1976, but was defeated by Jimmy Carter. Johnson was eligible to be elected to two full terms in his own right, as he had served less than two years of Kennedy's unexpired term, whereas Ford was eligible to be elected to only one full term, as he had served more than two years of Nixon's unexpired term.
President of the United States
Some presidents have had significant careers after leaving office. Prominent examples include William Howard Taft's tenure as Chief Justice of the United States and Herbert Hoover's work on government reorganization after World War II. Grover Cleveland, whose bid for reelection failed in 1888, was elected president again four years later in 1892. Two former presidents served in Congress after leaving the White House: John Quincy Adams was elected to the House of Representatives, serving there for seventeen years, and Andrew Johnson returned to the Senate in 1875. John Tyler served in the provisional Congress of the Confederate States during the Civil War and was elected to the Confederate House of Representatives, but died before that body first met.