In 1978, Peck traveled to Alabama, the setting of "To Kill a Mockingbird", to campaign for Democratic U.S. Senate nominee Donald W. Stewart of Anniston, who defeated the Republican candidate, James D. Martin, a former U.S. representative from Gadsden. In 1987, Peck undertook the voice-overs for television commercials opposing President Reagan's Supreme Court nomination of conservative judge Robert Bork. Bork's nomination was defeated. Peck was also a vocal supporter of a worldwide ban of nuclear weapons, and a life-long advocate of gun control.