Cooley challenged two-term incumbent District Attorney Gil Garcetti in the 2000 election. Garcetti and Cooley had a longstanding personal and professional rivalry, going back to at least 1996 when Cooley supported Garcetti's opponent for re-election, John Lynch. Garcetti defeated Lynch by a margin of approximately 5,000 votes out of slightly more than 2.2 million votes. After the election, Garcetti demoted Cooley from a supervisory position to the county's obscure Welfare Fraud division. The move mirrored Garcetti's demotion as the chief deputy for the entire county in 1988 by then-incumbent Ira Reiner, which caused Garcetti to challenge his former mentor and defeat him in the 1992 general election.