Lederer was elected to the Pennsylvania House of Representatives, where he served from 1974 to 1977. Lederer represented the same part of Philadelphia that had been served by both his father, Miles, and older brother, William. His sister-in-law, Marie, would also go on to serve in the State House.
Congress
Lederer was elected to Congress in 1976 to represent ; Lederer won with 73% of the vote, defeating Republican candidate Terence J. Schade. He took office on January 3, 1977. While serving on the House Ways and Means Committee, he was able to direct shipments of fruit from Chile to be imported through the Port of Philadelphia. Lederer was re-elected in 1978 with almost 72% of the vote over Republican Raymond S. Kauffman.
Abscam
Lederer was videotaped at a motel in New York on September 11, 1979, at a meeting with two undercover agents who presented themselves as representatives of a supposed Arab sheik. Accepting $50,000 in cash, he told the agents "I can give you me" in exchange for the money. After being implicated in the Abscam sting, Lederer was convicted of bribery on January 9, 1981, and sentenced to three years in prison and fined $20,000. Despite his indictment in the scandal, Lederer was re-elected, unlike the other members of the House implicated in the Abscam scandal. In the 1980 race, Lederer won with 54.5% of the vote, defeating Republican William J. Phillips, who had 32.8%, Consumer Party candidate Max Weiner with 9.5% and Independent John Morris with 3.2%. The United States House Committee on Standards of Official Conduct voted to expel him on April 28, 1981. Lederer resigned the following day, citing "personal legal problems" that interfered with his ability to serve his constituents. Joseph F. Smith ran in the Democratic Party primary in a race to succeed Lederer in a special election. After losing in the primary to David B. Glancey, chairman of the Democratic City Committee, Smith ran in the July 1981 special election as both an Independent and as a Republican and defeated Glancey, having promised in his campaign to caucus with the Democrats if elected. Lederer served ten months in Allenwood Federal Prison. He later worked as a roofer. Lederer died on December 1, 2008, of lung cancer at age 70 and is interred at the Holy Sepulchre Cemetery in Cheltenham, Pennsylvania.