He entered politics as a Democrat in Philadelphia in the early 1960s, when he was an assistant district attorney who sent six Teamsters officials to jail for union corruption.
After working on the Warren Commission, he returned to Philadelphia and challenged his boss, James Crumlish, for district attorney in 1965. Specter ran as a Republican and was derided by Crumlish as "Benedict Arlen." But Crumlish lost to his protege by 36,000 votes.
It was to be the last time until 1980 that Specter would win an election to higher office, despite three attempts — a 1967 bid for Philadelphia mayor, a 1976 loss to John Heinz for Senate and a 1978 defeat by Dick Thornburgh for governor.
Specter lost re-election as district attorney in 1973 and went into private practice. Among his most notorious clients as a private attorney was Ira Einhorn, a Philadelphia counterculture celebrity who killed his girlfriend in 1977.
Finally, in 1980, Specter won the Senate seat vacated by retiring Republican Richard Schweiker, defeating former Pittsburgh Mayor Pete Flaherty.
After leaving the Senate in January 2011, the University of Pennsylvania Law School announced Specter would teach a course about Congress' relationship with the Supreme Court, and Maryland Public Television launched a political-affairs show hosted by the former senator.
A funeral was scheduled for Tuesday in Penn Valley, Pa., and will be open to the public, followed by burial in Huntingdon Valley, Pa.
He is survived by his wife, Joan, and two sons, Shanin and Steve, and four granddaughters.