Senate President pro Tempore James O. Eastland served as acting President of the Senate during the 1st ("odd") session of the 93rd Congress due to a vacancy in the Vice Presidency of the United States: from 10 October 1973 (Vice President Spiro T. Agnew having resigned) to 6 December 1973 (Gerald R. Ford having been confirmed by Congress as Vice President as per the provisions of the 25th Amendment to the U.S. Constitution); during this same period, House Speaker Carl Albert was next in line to the Presidency under the 1947 Presidential Succession Act.

Senate President pro Tempore James O. Eastland served as acting President of the Senate during the 2nd ("even") session of the 93rd Congress due to a vacancy in the Vice Presidency of the United States: from 9 August 1974 (Vice President Gerald R. Ford having succeeded to the Presidency upon the resignation of President Richard M. Nixon) to 19 December 1974 (Nelson A. Rockefeller having been confirmed by Congress as Vice President as per the provisions of the 25th Amendment to the U.S. Constitution); during this same period, House Speaker Carl Albert was next in line to the Presidency under the 1947 Presidential Succession Act.