After the assassination of President John F. Kennedy and the succession of Vice-president Lyndon B. Johnson to the presidency on 22 November 1963, Americans became concerned about the, issue of presidential succession. For the next fourteen months — until the inauguration of Johnson and his running mate, Hubert Humphrey, in January 1965 — the vice-presidency remained vacant. Most Americans were shocked to learn that if Johnson, who had suffered a serious heart attack in 1955, died during 1964, John McCormack of Massachusetts, the sevehty-three-year-old Speaker of the House of Representatives, would become president. Next in the line of succession was Carl Hayden of Arizona, the eighty-seven-year-old president pro tempore of the Senate. They were followed by members of the cabinet, listed in rankorder beginning with the secretary of state. Americans were also concerned about who was authorized to take over the president's duties if he were remporarily incapacitated, a...