Jeffrey Bruce Klein, one of four journalists who in 1976 founded the magazine Mother Jones, rooting it in the crusading left-wing politics of the 1960s, and who returned in 1992 as editor in chief to rebrand it for younger, more digital readers, died on March 13 at his home in Menlo Park, Calif. He was 77.

His sons, Jacob and Jonah, said the cause was complications of a nerve disease.

Mr. Klein was an East Coast transplant to the Bay Area, drawn in the midst of 1960s counterculture by the possibility that the era’s anti-establishment character could continue to drive the region’s lively left-wing journalism.

In 1974 he joined Adam Hochschild, Paul Jacobs and Richard Parker, all editors at the progressive magazine Ramparts, to plan a publication that would expand the left’s focus on government malfeasance to include corporate muckraking and the role of money in politics.

They called it Mother Jones, in honor of the fiery labor leader Mary Harris Jones. Working from a cramped office above a McDonald’s in San Francisco, they produced their first issue in 1976.

Mr. Klein was officially the magazine’s literary editor, though in practice he commissioned writers of all kinds.

“He energetically barraged every writer he could think of with phone calls and letters,” Mr. Hochschild said in an interview.

Among his first finds was a short memoir by the Chinese writer Li-Li Ch’en, which ran in the inaugural issue and won a National Magazine Award in 1977.

Mr. Klein also contributed features of his own, including one on the complicated relationship between the basketball player Bill Walton and Portland, Ore., where he played professionally for the Trail Blazers. Another article showed that Richard V. Allen, Ronald Reagan’s first national security adviser, had failed to disclose connections to the fugitive financier Robert Vesco — a revelation that contributed to Mr. Allen’s resignation in 1982.

In 1981, Mr. Klein left to become the editor in chief of San Francisco magazine. A few years later he founded West, the Sunday magazine of The San Jose Mercury News, where he cultivated an army of young journalists.

“He had this unlimited enthusiasm about whatever we wanted to work on,” one of those journalists, Susan Faludi, said in an interview. She added that he commissioned her to write stories that became the basis of her first book, “Backlash: The Undeclared War Against American Women” (1991).

By the early 1990s, Mother Jones was sagging, having fallen, in the eyes of many readers, into the rut of predictably left-leaning diatribes. It had once had as many as 238,000 subscriptions; that number had dropped by half.

Mr. Klein returned to the magazine in 1992, this time as its editor in chief. He brought a tech-savvy sensibility to its investigative coverage, with features on Silicon Valley and the 1990s internet boom. In 1998, he began a $3.5 million market-research campaign and a complete redesign. Subscriptions rebounded by 25 percent over the five years after he arrived.

Mother Jones was the first general-interest magazine to have a substantial website. In 1994, Mr. Klein published an online database of corporate political donors, cross-referenced with their recipients.

His criticism was bipartisan: Though he took glee in going after Newt Gingrich, the Republican speaker of the House from 1995 to 1999, he was almost as savage in his attacks on Bill Clinton, whom he described as a “stunningly disappointing president.”

With an eye toward attracting new readers, Mr. Klein also ran articles that pushed against liberal orthodoxies, like one that was critical of affirmative action, and on matters outside the magazine’s core interests, like spirituality.

Such articles caused a rift between Mr. Klein and several members of the Mother Jones board, who wanted to hew closer to the progressive line. He resigned in 1998.

Jeffrey Bruce Klein was born on Jan. 15, 1948, in Scranton, Pa. His father, Harold, was a doctor, and his mother, Helen (Blum) Klein, managed the home.

He studied psychology at Columbia University and graduated in 1969; despite his left-wing politics, he did not participate in the protests that rocked the school while he was there.

He did, however, study under the famed literary scholar Lionel Trilling, an experience he later cited as critical to his decision to become a writer.

After graduating, like countless idealistic young people at the time, he packed up his Volkswagen Beetle and drove to California. He would live there for the rest of his life.

He studied education at Stanford, where he met Judith Weinstein. They married in 1971. She died in 1996. A second marriage, to Judi Cohen, ended in divorce.

He married Claudia Brooks in 2020. Along with his sons, both from his first marriage, she survives him, as do four grandchildren; his sister, Carol White; and his brother, Ken.

After leaving Mother Jones in 1998, Mr. Klein taught journalism at Stanford and worked as a producer for “PBS NewsHour” with Jim Lehrer. One of his “NewsHour” programs, on the Chinese economy, won a Gerald Loeb Award in 2006.

In between editing investigative journalism, he wrote a science fiction thriller, “The Black Hole Affair” (1991).

And while his pragmatism irked some of his friends on the left, he saw politics differently.

“There is obviously a left and right dimension, but I think the more critical dimension is outsider and insider,” he told The New York Times in 1993. “I think that is where the real political battles are.”