Bono, who followed her late husband Sonny Bono into Congress in the special election following his death, said that her rising seniority and the rigors of raising the funds for an effective campaign weighed against a senate bid.
Some California political operatives considered Bono, a GOP moderate, as a potentially strong threat to the very liberal Boxer.
Republicans currently in the race include former U.S. Treasurer Rosario Marin and state Assemblyman. Tony Strickland. Also on the list of potential GOP candidates are former Secretary of State Bill Jones and state Sen. Tom McClintock, who recently finished third in the race to replace recalled Gov. Gray Davis.