In 1970, when he was 36, Mr. Tunney ran for the Senate. He was blessed with a weak Republican opponent, the one-term incumbent George Murphy, a former actor and song-and-dance man whose age — he was in his late 60s — and health were issues. Mr. Murphy was also hurt by the revelation that while a senator he had been paid $20,000 a year as a public relations consultant for a movie company.
Mr. Tunney’s victory margin in 1970 was bigger than that of Ronald Reagan, who was re-elected California governor that year. Soon, Mr. Tunney was being mentioned as a possible running mate of Senator Edmund S. Muskie of Maine, who seemed to have the inside track for the Democratic nomination to run against President Richard M. Nixon in 1972. But Mr. Muskie’s campaign flamed out early in 1972.
That summer, Robert Redford starred in “The Candidate,” a film based on Mr. Tunney’s 1970 campaign, and the senator still appeared to have a bright future.
In 1974, the independent California Poll showed him to be more popular than Mr. Reagan, then in his last year as governor. In 1975, Mr. Tunney led a successful fight in the Senate to cut off funds for covert military operations by pro-American rebels in Angola. Mr. Tunney and like-minded lawmakers feared that involvement in Angola could lead to a Vietnam-like quagmire in Africa.
But many liberal Democrats were disenchanted with him. They thought he had been too slow to turn against the Vietnam War, which he had supported early on, and they were disappointed by his refusal to embrace a boycott of California grapes by striking farm workers.
Liberals found a champion in Tom Hayden, the former campus radical, who challenged Mr. Tunney in the 1976 Senate Democratic primary. Mr. Hayden raised a lot of money and was a surprisingly effective campaigner, accusing Mr. Tunney of being beholden to big business, though Mr. Tunney had supported antitrust legislation as a senator.
Mr. Hayden also sought to turn Mr. Tunney’s…