In 1920, Moody served as Williamson County Attorney, a position he held for two years before becoming District Attorney in 1922. In 1923, Moody obtained an assault conviction against four members of the Ku Klux Klan for beating and tarring a white traveling salesman. The Texas Historical Commission wrote, "These trials were considered the first prosecutorial success in the United States against the 1920s Klan and quickly weakened the Klan's political influence in Texas." The Klan was very powerful in Texas, with an estimated 150,000 members in the state, including the national imperial wizard. Texas Klansmen included a US senator and the mayors of Dallas, Fort Worth, and Wichita Falls. The case was widely reported and gave him political momentum despite Klan opposition.