This politician, born in 1942, was elected to his third Senate term in 1984 for which party? 
United States Senate election in Delaware, 1984:  Incumbent Democratic Senator Joe Biden won re-election to a third term, defeating Republican challenger John M. Burris. Joe Biden: Joseph Robinette "Joe" Biden Jr. ( ; born November 20, 1942) is an American politician who was the 47th Vice President of the United States from 2009 to 2017.
Democratic