Since direct elections began in Colorado in 1912, there are only four instances of incumbent U.S. Senators losing to challengers. The first time was in 1918 when Lawrence Phipps (R) unseated U.S. Sen. John Shafroth (D). More than four relatively uneventful decades passed until Peter Dominick (R) defeated John Carroll (D) in 1962. In 1972, Floyd Haskell (D) narrowly defeated Gordon Allott (R) only to be unseated six years later by William Armstrong (R).