For the capital's showboat - a tough new captain. As Ralph Davidson, the no-nonsense former chairman of Time Inc., takes the helm at Washington's Kennedy Center, will he chart a change in course for national culture?

RALPH DAVIDSON, dry-fly caster and former chairman of Time Inc., has hooked another really big one this time. Earlier this month Mr. Davidson became an arts czar - the chairman of the John F. Kennedy Center for the Performing Arts, as its founder, Roger Stevens, after 17 years of a long-running hit. Davidson became captain of the white marble showboat on the Potomac, where glittering international names in theater, concerts, dance, opera, film, and chamber music routinely appear, from Mikhail Baryshnikov to Pl'acido Domingo.

Mr. Stevens, the founding father of Kennedy Center and legendary producer of 250 shows (including hits like ``Annie'' and ``Les Mis'erables''), is considered a hard act to follow. Davidson's longtime associate and friend Ed Ney, former chairman of the advertising agency Young & Rubicam, says, ``It's a challenge, a tough job'' following the man who invented Kennedy Center as surely as Thomas Watson invented IBM or Henry Ford the Ford Motor Company

Davidson is a tall, broad-shouldered guy with shaggy gray hair and a voice that sounds like Charlton Heston's - deep, resonant, and pure Californian.

``I'm not Roger Stevens; my management style is different, my personality is different,'' he says. ``Roger has put together a unique, marvelous place. I like to say this is the house that Roger built. And what we're trying to do - and what I'm going to do, specifically - is build on what already is one [great] performing arts center.''

Davidson is dressed in a gray and white striped shirt, his red paisley tie slightly askew, like a reporter on deadline. He has a ruddy, outdoorsman's complexion, wary blue eyes, a sort of ``Mr. Smith Goes to Washington'' boyish drive. He steps gingerly over the first few questions as if they were firecrackers that might explode under him.

``We will try to do the best, get the best, present the best,'' he says, ``and maybe push the frontier a little bit every now and then, maybe bring in some unusual and offbeat productions.''

At Kennedy Center, one of the most difficult roles for Davidson as chairman may be walking in the Stevens footsteps as producer extraordinaire, a Broadway insider with a longtime network of talent who could fill an empty theater with merely a snap of his fingers.

Davidson has no theatrical background. In our interview I asked whether he planned to hire a theatrical honcho with producing experience or do the booking job himself. ``The way the system is emerging, I will be doing that...,'' he said.

``A lot of the productions which will be produced at Kennedy Center are going to be plays by [people like] William Saroyan, Tennessee Williams; I'd like to see Neil Simon - plays that have got a proven track record. Also I'm going to bring in new and exciting playwrights and try to put on some of their productions.''

In our interview he said he wouldn't be daunted by ``dark theaters'' when a play folds unexpectedly, losing lots of money for the Kennedy. Just as he became chairman, that happened. An expensive touring production of ``Sleuth'' folded on the road just before opening at the center. Despite Davidson's efforts, the Eisenhower Theater will remain dark for over a month until previews for a previously scheduled Stevens favorite, ``Sullivan and Gilbert,'' begin Sept. 7.

A spokesman for Kennedy Center says that, ``with the passing of the [chairman's] torch, Stevens also passed the theatrical responsibility on to Davidson as well. He now feels it's Davidson's turn.'' Since the ``Sleuth'' vacancy, Davidson has decided to hire a general manager with a theatrical background to run the production side and is advertising for one. His attitude: ``I'm not afraid to make a mistake, not afraid to put on something that flops. On the other hand, I hope that I, too, will find an `Annie' or a `Les Miz,' or what have you.''

At Kennedy Center, where ``The Mystery of Edwin Drood'' played (as ``Drood!'') this spring, the real mystery is what the new boss is like. Mr. Ney, who has known Davidson professionally and personally for 20 years, says, ``Ralph is a strong person with definite ideas about how things should be done, a guy with wide experience, a Californian, a Stanford graduate, with service in the CIA and experience in publishing and all sorts of things. To be chairman of Time Inc. is one of the great jobs in America.''

Ney says that Davidson has ``a keen mind. He's articulate, doesn't suffer fools gladly, and he can fight and argue with you. He's a fine athlete, beats me in tennis.'' But in life, says Ney, ``Ralph is not playing games. What you see is what you get. He's a very straight-ahead person. A lot of people think he's blunt at times, but he says what he means ... and doesn't try to color it up with a lot of soft phrases.''

Ney says that, in working with him as head of the advertising firm that handled the Time Inc. account, ``I found he was a hard-driving guy who got results, was generally popular with the people he worked with, knew what he was doing.'' He goes on to characterize Davidson as ``fiercely competitive,'' adding: ``He goes at life the way he skis - downhill, full blast. He's in the office 12 hours a day. He may not always be right; he may turn people off; he may be tough and blunt, but that's the Ralph Davidson I know. He's a tough guy, some people would say too tough.''

When he was Kennedy Center president, Davidson bumped the Twyla Tharp Dance Company and the Washington Ballet out of the center's Eisenhower Theater to make way for a more lucrative Lily Tomlin show. ``Lily Tomlin puts a lot of people in the seats,'' Davidson explained with a bluntness that alienated some dance lovers.

Davidson raised backing for this summer's San Francisco Arts Festival at the center and applauds more regional festivals here: ``I know from talking to people that there are some folks that are put off,'' he says. ``They think it's a little too formidable to come to the Kennedy Center. You know, `If you don't enjoy watching the New York City Ballet, there's nothing for you at Kennedy Center.' Nonsense, there's a lot of things for a lot of people here. ... I feel that we need to get that point of view across.''

There is little doubt that Davidson is a cultural pragmatist, a bottom-line guy, as interested in revenues and corporate funding as in programming. When he took the Kennedy Center job, he was chairman of the executive committee of the Business Committee for the Arts, had been a director of the New York City Ballet for seven years, and had raised funds for the Metropolitan Museum of Art as well as the Museum of Modern Art.

Davidson, as chairman of Kennedy Center, may put his stamp on national culture for years to come. In the arts world, the job is comparable to that of a Supreme Court justice, whose opinions and tastes can help shape the performing the arts through several administrations, as Stevens has from Kennedy through Reagan.

When it was first announced that Davidson would succeed Stevens, board member Daniel Boorstin, who cast the sole dissenting vote, went public on why he objected to Davidson. Mr. Boorstin, former librarian of Congress, said, ``The point I was trying to make is that the cultural institutions stand for things that are substantive, not mechanical and administrative. I would be happier to see the Kennedy Center in the hands of someone distinguished in the performing arts rather than someone with administrative and business talents.'' (Davidson brings up that line in pique; he knows it by heart.) Boorstin maintained that putting a money-raiser at the top is upside down. Several attempts to reach Boorstin for a current comment were unsuccessful.

Believes in corporate giving to the arts

Corporate support for the arts is a boon, Davidson says. ``It makes for a better and stronger community, which has got to be good for your business. So I'm a staunch supporter of business's giving to the arts. I'm also very strong in my belief that a corporation should have no influence on what the show is going to look like, or contain, or feel like, or whatever.''

Davidson reluctantly admits ``there's some truth'' to arts advocates' criticisms that corporate giving sometimes results in the safest, least experimental subjects being backed to enhance the corporate image. But he points out that corporations also have a responsibility to their shareholders ``to make con-tributions to the arts that are going to be in things that are very popular.''

Davidson intends to double the amount of corporate funding for Kennedy Center, from $2.5 million to $5 million. ``That's not out of line to ask for from the corporations of America. ... They do benefit from it. ... They have a tremendous involvement here with what goes on legislatively, who the administration is.''

Aims to triple endowment

Davidson also wants the National Endowment for the Arts to pony up considerably more than the $1 million in matching funds it currently gives to the Kennedy's endowment fund. ``I don't think that is in proportion to what the Kennedy Center provides in the way of the performing arts,'' he says. One of his big priorities is to expand the endowment fund from $25 million now to between $75 million and $100 million.

Hedley Donovan, former editor in chief of Time magazine, describes Davidson as ``a very capable executive, who would be very good at money-raising.'' Mr. Donovan, also describes him as ``a superb kind of Time Inc. ambassador, very attractive, personable, charming, a good speaker, a gregarious, likable man.''

Davidson was not amused by a Washington Post profile of him in which anonymous Time sources described him as a ``lightweight'' and not particularly popular with some of those who worked for him. Donovan, Ney, and William Kelly, former worldwide sales director for Time Inc., contradict that. Mr. Kelly, the retired publisher of Money magazine, says, ``He gets great loyalty from the people who work for him. When you need him, he's there. He's unflappable. You'd never know there are crises with Ralph; he takes all the burden himself; he handles it. He's very cool under fire.''

That sort of hang-tough self-confidence seems to come easy for a man whose closest friends describe him as a man's man. His old college chum from Stanford University, William Sarnoff, who made a cold, hard climb up Mt. Rainier with him, says, ``He's a wonderful guy to have on the other end of the rope.'' Mr. Sarnoff, chairman of Warner Publishing Inc., a division of Warner Communications, describes Davidson as ``very honorable, forthright.''

Another friend notes that Davidson was cool under the flak he received from some executives at Time Inc. for his early CIA experience, flak that came when the agency was under congressional investigation. Davidson says he worked for the CIA in covert operations in the Middle East-North African department. ``At the time I worked [there], working for the CIA was highly regarded,'' Davidson says. ``You were serving your country. ... I like serving my country. That's one of the reasons I took this job at Kennedy Center, because I looked at it in a sense of public service.''

Ralph Parsons Davidson was born in Santa Fe, N.M., but lost his father at 5 and was brought up in Los Angeles after his mother's remarriage. He was a surfer, president of his senior class at University High School, then president of the student body at Stanford, where he received a BA in international relations. After the Navy, he did a stint with the Marshall Plan in Europe before joining Time Inc. for a 34-year career.

Davidson, a registered Republican, has two sons - Will, 36, and Andy 32 - from his first marriage to Jeane Davidson. When he married former Texan Lou Hill, he also took on the role of father to her children - Ross, 19; Scott, 18; and Sydney, 11; they now have a fourth child, Mary Elizabeth, 3. Both Ralph and Lou Davidson's previous marriages had ended in divorce. They met at a New York dinner party given by the Sarnoffs, who told the reluctant Ms. Hill to show up ``because you're going to meet the man you're going to marry.''

An energy level that's `exasperating'

Right now the Davidsons are unpacking their lives in a handsome, rented Georgetown mansion filled with chintzes and art from the American West. Mrs. Davidson, a vivacious blonde with a face like a Sargent portrait, is a former Texas Christian University homecoming queen and a Democrat who worked for Lyndon Johnson in Washington. She is also a former elementary school teacher, who has worked quietly behind the scenes establishing an organization to aid homeless children.

She says of her husband, ``When he married me, the mother of three children, he not only took them on; he has risen to occasions for these kids that I don't think other fathers would.'' She mentions his compassion: ``Anytime there's an injustice, he becomes so activated he wants to find a way to right the injustice.'' Of Davidson, who may rise at 6 a.m., do errands, and play tennis before working till midnight, she says, ``There is an energy level that is exasperating.'' He relaxes with thrillers and western novels by Louis L'Amour.

Vernon Jordan Jr., another longtime friend and former chairman of the Urban League, found Davidson as a member of its board of trustees ``creative, energetic, committed, hard-driving. He's also caring and warm. I was in the hospital for 84 days [recovering from a gunshot attempt on his life], and he came a lot - sometimes said something, sometimes didn't, but he was there. That is a very human side of him.''

As Mrs. Davidson puts it, ``He's not a man's man; he's a human being's man.''

Second in an occasional series of profiles of influential figures in the arts. The first, an interview with Roger Stevens, was published May 23.