(Reuters) - Veteran social activist and politician Tom Hayden, a stalwart of America’s New Left who served 18 years in California’s state legislature and gained a dash of Hollywood glamour by marrying actress Jane Fonda, has died aged 76, according to media reports.

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Hayden died in Santa Monica, California, after a long illness, The Los Angeles Times reported on its website.

“A political giant and dear friend has passed,” Los Angeles Mayor Eric Garcetti wrote on Twitter, adding “Tom Hayden fought harder for what he believed than just about anyone I have known.”

Hayden, who forged his political activism as a founding member of Students for a Democratic Society, which stood at the core of the 1960s anti-war and civil rights movements, was principal author of the group’s revolutionary manifesto, the Port Huron Statement.

The University of Michigan student ventured into the Deep South, where he joined voter registration campaigns and was arrested and beaten while taking part in the “freedom rider” protests against racial segregation.

Hayden, however, became perhaps best known as one of the “Chicago Eight” activists tried on conspiracy and incitement charges following protests at the turbulent 1968 Democratic National Convention. He was ultimately acquitted of all charges.

A New York Times book review of his 1988 memoir, “Reunion,” one of more than 20 books published under his name, called Hayden “the single greatest figure of the 1960s student movement.”

Outliving contemporaries Abbie Hoffman, Jerry Rubin, Eldridge Cleaver and Huey Newton, Hayden remained active in left-wing politics well into the 21st century, posting on Twitter just a week ago.

Winning election himself to the California state Assembly in 1982, and then the state Senate a decade later, Hayden went on to serve a total of 18 years.

Later he became director of the Peace and Justice Resource Center, a nonprofit left-wing think tank devoted mainly to analysis of continued U.S. military involvement in Iraq, Afghanistan and Pakistan, drug policy and global poverty.

Hayden was married to actress Jane Fonda from 1973 to 1990, with whom he had two children. Midway through their marriage, the couple graced the cover of People Magazine.

In later years his writings were published in national publications including The New York Times, the Boston Globe and the Denver Post. He served on the editorial board and was a columnist for The Nation magazine, and was the author of more than 20 books.

Tributes poured in on social media, including from actress Martha Plimpton, who wrote on Twitter: “Rest in peace, Tom Hayden. And thank you. Love to all who knew & worked w him. Esp his family, and @Janefonda. He was a good man.”