In 1990, Jim Gerlach was elected to the Pennsylvania House of Representatives by a margin of 23 votes out of 17,000 votes cast in the 155th State Representative District. He defeated the 18-year incumbent.
In 1992 he was re-elected to the Pennsylvania House of Representatives by a margin of 64 to 34 percent.
In 1994, he was elected to Pennsylvania State Senate by margin of 67 to 33 percent. In 1998, he was re-elected without opposition to 2nd term in Pennsylvania State Senate.
He was elected to Congress in 2002 with 51 percent of the vote in an open race against Democrat Dan Wofford, the son of former Sen. Harris Wofford. The seat was drawn for Gerlach, and includes 50,000 more registered Republican voters than Democrats.
Gerlach ran unopposed in the 2004 Republican primary and faced Democrat Lois Murphy in the fall general election.