Democrat Robert Byrd was the longest serving senator (1959-2010) at the time of his death in 2010. He was also a Grand Wizard with the KKK.
"The Klan is needed today as never before, and I am anxious to see its rebirth here in West Virginia and in every state in the nation."
I shall never fight in the armed forces with a negro by my side ... Rather I should die a thousand times, and see Old Glory trampled in the dirt never to rise again, than to see this beloved land of ours become degraded by race mongrels, a throwback to the blackest specimen from the wilds.
— Robert C. Byrd, in a letter to Sen. Theodore Bilbo (D-MS), 1944