In 1972, Williams ran in the Democratic primary for the U.S. Senate seat formerly held by the late Richard Russell, Jr. He polled 46,153 votes (6.4 percent). The nomination and the election went to fellow Democrat Sam Nunn. In 1974, Williams was elected to the Georgia Senate where he served five terms as a Democrat, until 1984. In 1985 he was elected to the Atlanta City Council, serving for five years, until his election in 1989 when he ran for Mayor of Atlanta but lost to Maynard Jackson. That same year Williams successfully campaigned for a seat on the DeKalb County, Georgia County Commission which he held until 1994. Williams supported former Georgia Governor Jimmy Carter for president in 1976, but surprised many black civil rights figures in 1980 by joining Ralph Abernathy and Charles Evers in endorsing Ronald Reagan. By 1984, however, he had soured on Reagan's policies, and returned to the Democrats to support Walter F. Mondale.