The current situation is unusual. Theodore Roosevelt, Calvin Coolidge, Harry Truman, and Lyndon Johnson all stepped down after one elected term -- but all four had been vice presidents who assumed the presidency after their predecessors died. (TR would run again in 1912.) One has to go back to Rutherford B. Hayes to find a president who voluntarily retired after four years. His vice president, William Wheeler, also declined to run in the election of 1880
