Special election to fill vacancy caused by death of Robert Kerr on January 1, 1963. Outgoing Governor J. Howard Edmondson was initially appointed to the seat, but was defeated by Fred Harris in the Democratic runoff primary in May 1964.
Source for Popular Vote data: Oklahoma State Election Board, comp, "United States Senator (Unexpired Term)," State of Oklahoma Election Results and Statistics 1964 (Oklahoma City, 1964)