Richard Dysart had an extensive list of credits on stage and screen. (Nick Ut/AP)

Richard Dysart, an actor whose quiet air of authority helped him play presidents, generals, corporate executives and his best-known character, low-key senior partner Leland McKenzie of “L.A. Law,” died April 5 at his home in Santa Monica, Calif. He was 86.

He had cancer, said his wife, Kathryn Jacobi Dysart.

Mr. Dysart was a veteran of the Broadway stage and had appeared in many movies, but he didn’t land his trademark role until he was in his late 50s. “L.A. Law,” a legal drama spiced with sex and dark humor, ran on NBC from 1986 to 1994 with a cast that over the years included Harry Hamlin, Corbin Bernsen, Jimmy Smits, Susan Dey, Michael Tucker and Jill Eikenberry.

As his firm’s founding partner, Mr. Dysart’s character was a voice of calm and probity amid office rivalries, sizzling affairs, toxic clients and brutal courtroom battles.

Mr. Dysart’s work on “L.A. Law” brought him a 1992 Emmy for best supporting actor as well as unending invitations to bar association luncheons. In 23 states, he recorded public service messages urging attorneys to do more pro bono work for the poor.

He also used several “L.A. Law” episodes to battle the sense of shame experienced by many people with hearing problems. In one of them, Leland McKenzie argued an age discrimination case in court wearing the hearing aids that Dysart himself had started to use several years earlier. He won the case.

By its second season, “L.A. Law” was a favorite of attorneys for what Michael J. Kelly, then dean of the University of Maryland Law School, called its “flavor of reality” — its depiction of office flirting, balky phone systems and difficult clients. Law students loved it, he said, partly because of “the inspiration it gives them for the infinite possibilities of sex.”

Even staid old Leland was swept into a whirlpool of passion. In a memorable 1991 scene, he tries calmly and reasonably to part with his ex-lover, played by Diana Muldaur, moments before she accidentally plunges down an elevator shaft.

“It was the moment,” TV Guide critic Jeff Jarvis wrote, “that the show lost us, when it went too far and broke the spell.”

As the series ended in 1994, Mr. Dysart told interviewers that it had veered too much “from the courtroom into the bedroom.”

“It’s the right time to end it,” he said.

Born in Brighton, Mass., on March 30, 1929, Richard Allan Dysart grew up in Maine, where as a boy in Skowhegan he was entranced with radio. When he was 16, he narrated the farm report — “the price of butter and eggs with everything I could give,” as he later described it — on an Augusta, Maine, radio station.

He studied speech communications at Emerson College in Boston, leaving as an undergraduate for a four-year stint in the Air Force. After returning for his bachelor’s and master’s degrees, he headed for New York and the life of a struggling actor.

At the famed Circle in the Square theater, he sold tickets part time but also became an understudy in Eugene O’Neill’s tragedy “The Iceman Cometh.” After his first performance, his fellow actors applauded him, his wife said.

He went on to star in numerous productions on and off Broadway, including about 500 performances as Coach in the Pulitzer Prize-winning play “That Championship Season” by Jason Miller. He also was a founder of the San Francisco-based American Conservatory Theater.

In films, Mr. Dysart appeared as a U.S. secretary of defense in “Meteor” (1979) and as the ill-fated captain Ernst Lehmann in “The Hindenburg” (1975). He was President Truman in two TV movies; Ulysses S. Grant in a 1977 drama about Gen. George Armstrong Custer; and Gen. Dwight D. Eisenhower in “Churchill and the Generals,” a 1979 BBC production.

In the 1987 film “Wall Street,” he played the chief executive of a company besieged by Gordon (“Greed is good”) Gekko.

His favorite role, his wife said, was as Dr. Robert Allenby, a kind-hearted physician in the quirky 1979 Peter Sellers comedy “Being There.”

In addition to Kathryn Jacobi Dysart, his wife since 1987, survivors include a stepson and two grandchildren. Two previous marriages ended in divorce.

— Los Angeles Times