Jerry Costello won a seat in the U.S. House in an August 1988 special election to fill a vacancy left by the death of Democratic Rep. Melvin Price. He defeated Republican Robert H. Gaffner with 51 percent of the vote. Costello then went on to win a full term in November 1988 against Gaffner with 53 percent of the vote and has been re-elected ever since.
In 1990, he defeated Gaffner again with 66 percent of the vote. He won re-election in 1992 with 71 percent of the vote, defeating Republican Mike Starr.
He was re-elected in 1994 with 66 percent of the vote, defeating Republican Jan Morris. In 1996, he was re-elected with 72 percent of the vote, defeating Republican Shapley Hunter.
Costello was re-elected in 1998, defeating Republican Bill Price with 60 percent of the vote. Price, the son of Costello's predecessor, had switched parties. In 2000, Costello was re-elected in an uncontested race.
He was re-elected in 2002 with 69 percent of the vote against Republican David Sadler.
Costello was elected in 1980 to a two-year term as St. Clair County Board chairman, and won re-election, to four-year terms, in 1982 and 1986.