He had been diagnosed two weeks ago with lymphoma, said his wife, Kirsten Liegmann.
Along with organizers such as Tom Hayden, Mr. Davis was an early leader of the Students for a Democratic Society, a wide-ranging activist organization that became a defining element of the New Left. Mr. Davis assisted Hayden in drafting the 1962 Port Huron Statement, the founding document of the SDS, and he remained a force on the political scene through the rest of that decade.
With his short hair and bookish glasses — a Washington Post reporter once described him as looking “more like a seminarian than a revolutionary” — Mr. Davis appeared at least superficially to be an outlier among his more hirsute colleagues.
The son of a top economist in the Truman administration, he had grown up in the Washington suburbs and then on his family’s chicken farm in rural Virginia, where, he boasted years later, he became the chicken-judging champion of the Middle Atlantic.
He turned to activism as a student in the late 1950s and early ’60s at Oberlin College in Ohio, where he joined the SDS and initially occupied himself with efforts to bring about greater economic equality in poor communities.
“He was profoundly committed to mobilizing people and very skilled at it, very articulate, very well-organized — an interesting combination of somebody who had oratorical skill and at the same time organizational smarts,” said Todd Gitlin, a former SDS leader, professor at Columbia University and author of books including “The Sixties: Years of Hope, Days of Rage.”
Gitlin described Mr. Davis as “very personable and magnetic,” someone who “recruited supporters with ease.”
Mr. Davis’s interests gradually expanded to include marshaling opposition to U.S. involvement in the Vietnam War. Tensions over the conflict boiled over at the 1968 Democratic convention in Chicago as Vice President Hubert Humphrey defeated U.S. Sen. Eugene McCarthy (D-Minn.), who had campaigned on an antiwar platform, for the Democratic presidential nomination.
Thousands of demonstrators had gathered in Chicago, where violent confrontations with police and the National Guard ensued. Mr. Davis recalled being struck in the head and knocked to the ground. “I was on the ground crawling with my two arms trying to get away and just being clubbed and clubbed and clubbed,” he told the Guardian newspaper of London years later.
A federal commission convened to review the incident described the events as tantamount to a “police riot,” with law enforcement officials responding in disproportionate fashion to the actions of protesters, some of whom were peaceful and some of whom were seeking to provoke.
The next year, Mr. Davis was among eight defendants — the others included Hayden, Abbie Hoffman, David Dellinger, Jerry Rubin, Lee Weiner, John Froines and Bobby Seale — indicted on charges stemming from a conspiracy to incite a riot. They were known initially as the Chicago Eight and became the Chicago Seven after the charges against Seale, a Black Panther leader, were moved to separate proceedings and eventually dropped.
“In choosing the eight of us, the Government has lumped together all the strands of dissent in the sixties,” Mr. Davis told the New York Times. “We respond by saying the movement of the past decade is on trial here.”
The dramatic, at times circuslike courtroom saga held national attention on the Chicago Seven for months. Five of the defendants, including Mr. Davis, were convicted of crossing state lines with the intent to incite a riot. They appealed, and in 1972 a court overturned the convictions in a decision that criticized conduct by the judge and the prosecutor.
Decades later, the trial remains the subject of abiding public fascination. A film about the episode, “The Trial of the Chicago 7,” written and directed by Aaron Sorkin and featuring actor Alex Sharp as Mr. Davis, was released last year.
As the 1960s gave way to the ’70s, Mr. Davis appeared to become increasingly militant, particularly in his opposition to the Vietnam War. In 1970 he told a gathering of Columbia students that if the 1960s had called for sit-ins, then the new decade demanded the burning of banks.
“If this generation is to survive,” he said, according to an account in the Times, “it has to begin to fight.”
Traveling to communist North Vietnam, he later wrote, he “started to feel like someone who had slipped into one of the American colonies from Great Britain to witness a small band of freedom fighters during our own country’s war of independence.” In 1971 he helped organize the May Day demonstrations in Washington, where protesters — thousands of whom were arrested — erected barricades throughout the District to voice their opposition to the war.
Two years later, Mr. Davis announced that he planned to forgo traditional activism and pursue a more just social order as a devotee of Guru Maharaj Ji, a 15-year-old Indian mystic who had cultivated an international following.
“I would cross the planet on my hands and knees to touch his toe,” Mr. Davis said in 1973, describing the guru’s teachings as a “practical way to fulfill all the dreams of the movement of the early sixties and seventies.”
The announcement prompted bewilderment among admirers as well as critics.
“It was one thing for Tom Hayden to marry a well intentioned if slightly flat-headed movie star,” journalist Nicholas von Hoffman wrote in The Post, referring to Hayden’s marriage to actress Jane Fonda, “or some of the other movement heavies to turn into the psychological basket cases a number have become.”
But “Rennie,” von Hoffman continued, “was the most stable, the calmest, the most enduring of that group of young people who set out to change America at the beginning of the 1960s.”
Von Hoffmann attributed Mr. Davis’s conversion at least in part to the dissolution of the protesters who had once surrounded him.
“In the spring of 1970, this generation believed it could overcome all,” von Hoffman quoted Mr. Davis as saying, “but then came the summer . . . drift and no direction and by the fall of 1970 we really did lose the generation. The activists continued but after that it wasn’t the same. People went into the country, they were into drugs and into themselves.”
Rennard Cordon Davis was born in Lansing, Mich., on May 23, 1940. He attended high school in Clarke County, Va., where he was student body president, worked on the newspaper and yearbook, and played varsity basketball in addition to his activities with the 4-H club.
He graduated from Oberlin in 1962 and later received a master’s degree in labor relations from the University of Illinois. At the start of his involvement with the SDS, he led the Economic Research and Action Project, an initiative that placed activists in low-income communities and sought to organize what they described as an “interracial movement of the poor.”
Mr. Davis’s marriages to Luane Abend and Valerie Albicker ended in divorce.
Besides Liegmann, whom he married in 2018, his survivors include a daughter from his first marriage, Lia Davis of Lakewood, Colo.; two children from his second marriage, Maya Davis of Boise, Idaho, and Sky Davis of Denver; a sister; two brothers; and two grandchildren.
At the time of his death, Mr. Davis was chairman of a foundation established, according to its website, to remake a human society that has become “a wrecking ball to every natural living system” and to forge “an unstoppable force for a new way of living on Earth.”
“I try not to be reckless,” he had told in The Post in 1971, “and try to avoid confrontations that can lead to prison or death, but I’ll never stop working. . . . I’m really pulled toward a life that lets you keep in touch with yourself.”