WASHINGTON — The legacy of six-term Sen. Richard Lugar is the creation of a program that helped the former Soviet states destroy their weapons of mass destruction.

The 80-year-old Republican, turned aside by Indiana primary voters Tuesday, also valued cooperation over confrontation. His defeat is a blow to the center of the Senate as moderates have decided to retire and others are vulnerable this election year.

Lugar's singular achievement in a 36-year Senate career was the program to help former Soviet states dismantle nuclear, chemical and biological weapons. He worked on legislation to create the program in 1991 with former Democratic Sen. Sam Nunn of Georgia.

Nunn said in an interview that the two worked together but Lugar never compromised his principles.