DENVER (AP) — Ben Nighthorse Campbell, the former senator and U.S. representative of Colorado known for his passionate advocacy of American Indian issues, died Tuesday. He was 92.

Campbell died of natural causes surrounded by his family, his daughter, Shanan Campbell, confirmed to The Associated Press.

Campbell, a Democrat who stunned his party by joining the Republican Party, stood out in Congress as much for his unconventional dress — cowboy boots, bolo ties and ponytail — as his defense of children’s rights, organized labor and fiscal conservatism.

A member of the Northern Cheyenne tribe, Campbell said his ancestors were among more than 150 Native Americans, mostly women, children and elderly men, killed by U.S. soldiers while camped under a flag of truce on Nov. 29, 1864. He helped sponsor legislation upgrading the Great Sand Dunes National Monument in southern Colorado, where the massacre happened, to a national park.

He served three terms in the House, starting in 1987. He then served two terms in the Senate, from 1993 to 2005.

The Associated Press