Ernest Istook was elected to the U.S. House in 1992 with 53 percent of the vote, defeating Democrat Laurie Williams. He was re-elected in 1994 with 78 percent of the vote, defeating independent candidate Tommy Keith. In 1996, he was re-elected with 70 percent of the vote against Democrat James Forsythe. Istook was re-elected in 1998, defeating Democrat M.C. Smothermon with 68 percent of the vote.
He was re-elected in 2000 with 68 percent of the vote. He won re-election in 2002 with 62 percent of the vote.
Istook was elected to Oklahoma House in 1986. In 1988, he was elected as the Assistant House Minority Leader.
He was re-elected in 1988 and 1990.