Senate President pro Tempore Carl Hayden served as acting President of the Senate during this "odd" session of the 88th Congress due to a vacancy in the Vice Presidency of the United States from 22 November 1963 (Vice President Lyndon Baines Johnson having succeeded to the Presidency upon the death of President John Fitzgerald Kennedy); during this same period, House Speaker John W. McCormack was next in line to the Presidency under the 1947 Presidential Succession Act.

Senate President pro Tempore Carl Hayden served as acting President of the Senate throughout this "even" session of the 88th Congress due to a vacancy in the Vice Presidency of the United States (Vice President Lyndon Baines Johnson having succeeded to the Presidency during the previous "odd" session); during this same period, House Speaker John W. McCormack was next in line to the Presidency under the 1947 Presidential Succession Act.