Key events in career of former Sen. Arlen Specter

— 1964: Serves on the Warren Commission, which concludes that a lone assassin killed President John F. Kennedy.

— 1965: Runs successfully on Republican ticket for Philadelphia district attorney, even though he was a Democrat.

— 1967: Loses election for Philadelphia mayor.

— 1969: Elected to second term as district attorney.

— 1973: Loses bid for third term as district attorney.

— 1976: Loses GOP Senate primary.

— 1978: Loses GOP gubernatorial primary.

— 1980: Wins Pennsylvania's open U.S. Senate seat and joins new Republican majority in the chamber.

— 1986: Elected to second term in Senate.

— 1987: Helps defeat President Ronald Reagan's Supreme Court nomination of Robert H. Bork.

— 1991: Aggressively questions Anita Hill during Clarence Thomas' Supreme Court nomination hearing.

— 1992: Elected to third term in Senate.

— 1995: Announces candidacy for president. Suspends campaign later that year amid fundraising difficulties.

— 1998: Elected to fourth term in Senate.