Sander Vanocur, a veteran broadcaster for NBC and other networks who covered the civil rights movement and Vietnam War and was part of the panel of interviewers at the first televised presidential debate, between John F. Kennedy and Richard M. Nixon in 1960, died Sept. 16 at a hospice center in Santa Barbara, Calif. He was 91.

The cause was complications from dementia, his son, Chris Vanocur, said.

Mr. Vanocur (pronounced van-OH-ker) was a familiar face on television news for decades, beginning when he joined NBC News in the late 1950s. While covering the 1960 presidential campaign, he had a historic role as one of four panelists asking questions of Kennedy and Nixon at their first debate.

The debate, held Sept. 26, 1960, in Chicago and watched by about 70 million people, was considered a turning point in the race and highlighted the growing influence of television.

Nixon had been ailing from a staph infection in his knee and came to the debate without rehearsing his responses. He turned down the offer of professional makeup, which left him perspiring and with a swarthy five o’clock shadow under the studio’s bright lights.

Mr. Vanocur put Nixon on the defensive when he cited President Dwight D. Eisenhower’s remark about ideas advanced by Nixon, his vice president. “If you give me a week,” Eisenhower said, “I might think of one. I don’t remember.”

Nixon brushed off Eisenhower’s comment as “probably a facetious remark.” But Nixon’s responses and appearance at the debate helped turn voters toward Kennedy, who projected a calm and comfortable manner and, by looking directly into the camera, had a better understanding of the demands of the new medium of television.

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“We did not see the debate as the rest of the country saw it,” Mr. Vanocur said in 2010 of the panel of journalists. “Those who heard it on the radio thought Nixon had won. In the studio, the four of us were seated on a platform, and we looked at the two candidates with our naked eyes.”

After Kennedy won a narrow victory in 1960, Nixon came to resent the debates and what he considered the triumph of showmanship over the exchange of ideas. After Nixon was elected president in 1968, he put Mr. Vanocur on the so-called White House enemies list.

Mr. Vanocur covered the Kennedy White House, accompanied first lady Jacqueline Kennedy on international tours and once received a curtsy from the president’s young daughter, Caroline, after he gave her a children’s book as a gift.

He later covered the growing U.S. military involvement in Vietnam and reported on the civil rights movement in the American South. In 1967, he conducted a revelatory interview with the Rev. Martin Luther King Jr., in which the civil rights leader confessed that the dream of equality he outlined in his famous 1963 speech on the steps of the Lincoln Memorial, had turned into a “nightmare.”

In the interview, less than a year before King was slain, he spoke of how the Vietnam War could “poison the very soul of our nation,” but he added that his commitment to nonviolence remained firm.

While covering the 1968 presidential campaign, Mr. Vanocur interviewed Sen. Robert F. Kennedy hours before the candidate was gunned down in the kitchen hallway of a Los Angeles hotel. Mr. Vanocur stayed on the scene for hours, covering the aftermath of the assassination.

Mr. Vanocur left NBC in 1972 to lead a short-lived news program with Robert MacNeil on PBS, then spent time at a think tank and teaching before joining The Washington Post in 1975 as a television columnist and editor.

In 1977, he went to ABC News, where among other assignments, he returned to his earlier experience in high-profile debates. He was the moderator of a vice presidential debate in 1984 and a panelist in a 1992 presidential debate between George H.W. Bush and Bill Clinton.

“Television has come to so dominate politics that the very act of political reporting becomes part of it,” Mr. Vanocur told the Los Angeles Times in 1991. “I’m not sure that’s good or bad. It’s just a fact.”

Sander Vanocur was born Jan. 8, 1928, in Cleveland. His father was a lawyer.

After his parents divorced in the early 1940s, he moved with his mother and sister to Peoria, Ill. His mother changed the spelling of the family’s last name from Vinocur to Vanocur.

Mr. Vanocur graduated in 1950 from Northwestern University in Evanston, Ill., then studied at the London School of Economics and served two years in the Army, primarily in Europe.

Before publishing an opinion piece in London’s Observer newspaper, he was planning to attend law school, but he later said he was so intoxicated by seeing his name in print that he decided to embark on a career in journalism.

He worked at the Manchester Guardian newspaper and occasionally as a London-based broadcaster for CBS and other news agencies before joining the New York Times as a metropolitan reporter in 1955. He moved to NBC two years later, assigned to the Washington and Chicago bureaus.

Later, during his 15 years at ABC, Mr. Vanocur held several positions, including chief diplomatic correspondent and anchor of a program on business news. He saw television news change from a slow-paced medium, in which he sometimes had a week to polish a story, to a form of nearly instantaneous communication. It was not an evolution he always liked.

“Now, we have the capacity because of technology to be almost everywhere almost at once,” Mr. Vanocur said in 1991, “and, because we are there, that in itself becomes significant. And, because everything’s significant, nothing is significant.”

His first wife, the former Edith Pick, a onetime food columnist for The Post, died in 1975 after 19 years of marriage. Their son, Nick Vanocur, died in 2015. Survivors include his wife of 43 years, the former Virginia Backus Wood, of Montecito, Calif.; a son from his first marriage, broadcast journalist Chris Vanocur of Salt Lake City; a stepdaughter, Daphne Wood Hicks of New York City; and two grandchildren.

After leaving ABC in 1992, Mr. Vanocur was a visiting scholar at the First Amendment Center in Nashville, where he developed educational videos on how presidents used radio and television through the years.

He sometimes appeared as himself in films and TV shows, including “Dave” (1993) and “Without Warning” (1994), a TV retelling of H.G. Wells’s “The War of the Worlds.” He later joined the History Channel, where he was the host of “Movies in Time,” in which he interviewed scholars and others about the historical accuracy and significance of various films.

Mr. Vanocur settled in California, but “mostly I live on United Airlines,” he joked.

Balding and slightly stocky, he bore a physical resemblance to another well-traveled television reporter, Charles Kuralt of CBS News.

“I was in an airport the other day and headed for the United club,” he told the St. Petersburg Times. “And as I pulled out my membership card the woman said, ‘Oh, you don’t need to do that, Mr. Kuralt.’ I just said thank you and walked on in.”

An earlier version of this story gave the wrong title for Robert F. Kennedy. He was a senator at the time of his death, not a U.S. representative.