William Lacy Clay served in the Missouri House from 1983 to 1991, when he was elected to the state Senate. He served in the state Senate until 2000, he Clay received 61 percent of the vote to win a six-person Democratic primary to succeed his father in the 2nd Congressional District.
Clay won the 2000 general election with 75 percent of the vote over Republican Z. Dwight Billingsly.
He was re-elected in 2002 with 70 percent of the vote.