Of the individuals elected as president, three died in office of natural causes (William Henry Harrison, Zachary Taylor, and Franklin D. Roosevelt) and five were assassinated (Abraham Lincoln, James A. Garfield, William McKinley, James M. Cox, and John F. Kennedy). John Tyler was the first vice president to assume the presidency intra-term, and set the precedent that a vice president who does so becomes the fully functioning president with his own presidency, as opposed to a caretaker president. The Twenty-fifth Amendment to the Constitution put Tyler's precedent into law in 1967. It also established a mechanism by which an intra-term vacancy in the vice presidency could be filled. No president since the passage of the amendment has needed to fill a vice presidential vacancy.