Table:
text: Earliest serving United States Senator
Earliest serving Senators currently living
Earliest serving Senators currently living
Rank_ Senator Date_of_birth Entered_Senate Left_Senate State_served Party Time_since_entry
20 Elaine S. Edwards March 8, 1929 August 1, 1972 November 13, 1972 Louisiana Democrat 41years, 184days
21 Sam Nunn September 8, 1938 November 8, 1972 January 3, 1997 Georgia Democrat 41years, 85days
22 Bennett Johnston Jr. June 10, 1932 November 13, 1972 January 3, 1997 Louisiana Democrat 41years, 80days
23 James Abourezk February 24, 1931 January 3, 1973 January 3, 1979 South Dakota Democrat 41years, 29days
23 Joe Biden November 20, 1942 January 3, 1973 January 15, 2009 Delaware Democrat 41years, 29days
23 Dick Clark September 14, 1928 January 3, 1973 January 3, 1979 Iowa Democrat 41years, 29days
23 Pete Domenici May 7, 1932 January 3, 1973 January 3, 2009 New Mexico Republican 41years, 29days

Question: To which part of the list of earliest incumbent United States Senators does Congressman Dick Clark belong?