Until the 25^th Amendment to the U.S. Constitution was ratified on February 23, 1967, there was no provision for filling a vacancy in the office of the Vice President. Consequently, there have been numerous instances when the position was left vacant for a period of months or even years.

Four U.S. Presidents to date served a full term in office without benefit of a sitting Vice President: John Tyler (1841-1845), Millard Fillmore (1850-1853), Andrew Johnson (1865-1869) and Chester A. Arthur (1881-1885).