Not long ago, Stuart J. Long, a chunky, 37-year-old with long hair and a droopy mustache, was just another pub owner in town.

Sure, he had three saloons and a restaurant on Capitol Hill as well as several pieces of real estate. But he could hardly be counted among the city's influential businessmen. He had no access to policy makers in the District Building. He didn't even bother with the Metropolitan Washington Board of Trade. And they didn't bother with him.

"They were basically a downtown organization. I'm over here on the Hill," Long said the other day. "Being on Capitol Hill in comparison to being downtown is about like being in Laurel."

So, long minded his businesses, catering to the growing group of young, middle-class Hill dwellers and workers, including a promising young street activist turned politician who lived in the neighborhood and came in frequently to do more talking than drinking -- Marion Barry.

Long's status changed dramatically last year when Barry was elected mayor. He had followed Barry's rise with interested and financial contributions as Barry climbed from being a street militant to the city's highest elected official. During the campaign for mayor, Long raised more than $40,000 for Barry.

Now he has access to the District's chief executive. He can ring Barry on the telephone and have his calls returned. He can drop by the District Building to see the mayor -- even though, as happened on one recent occasion, he runs the risk of having his Mercedes stolen off the parking lot while he hobnobs.

Barry had Long appointed to the D.C. Democratic State Committee, making Long a member of the in-crowd of District Democrats.

Barry appointed Long, an avid sports fan who gets good spinoff trade from major sporting events at nearby RFK Stadium, to serve on the three-member board that runs RFK and the D.C. Armory. Long spends some of his time these days working with Barry to try to return professional baseball to the city.

Stuart Long is one of a new generation of businessmen -- black and white -- who came into power with Barry, a new generation mayor. Long says Board of Trade Executive Vice-President John Tydings actively tries to get him involved in the organization, once the clubby preserve of big-time bankers, real estate magnates, lawyers and developers who lunched on Connecticut Avenue.

Long is not overwhelmed by such perks of power. He's cool, confident and even a bit cocky.

"They're a dying breed," Long said of the older group, with no apparent disdain in his voice. "They'll be around. But I don't think any of the younger businessmen are striving to be a Duke Zeibert. I'm not.

"For me to operate like them would be the same as asking Marion Barry to operate like Walter Washington."

Long is a homegrown boy, who was raised in nearby Greenbelt when it was just an experimental development.

Long made his first real money working construction and renovating houses on Capitol Hill just as the restoration boom was beginning in the early '60s. His original investment in the Hawk 'n' Dove in 1967 was $14,000.

Long estimates his worth now at more than $1 million -- not bad for an Irish lad from a family of 10, who says that as a kid he never lived in a house with more than one bathroom.

Anyone who has been to a bar or restaurant on the Pennsylvania Avenue strip near the Capitol has probably done business with Long. Along with a partner, he owns The Hawk 'n' Dove, Duddington's, Jenkins Hill and Yolanda's Al Campidoglio.

Long also owns two small apartment buildings which he plans to convert to condominiums. All in all, he employs about 250 people.

Like Barry, who is essentially a product of the past 15 years of politics and quasi politics in Washington, Long the businessman is a product of the past two decades of life in Washington.

As the restoration movement prospered on the Hill, so did Long. The younger, more affluent whites and blacks who restored or bought the new homes, the gays who migrated to the city, the childless professional couples -- all people who would become a part of Barry's political base -- added to his clientele. They gathered along with Capitol Hill regulars to sit on the wicker chairs under skylights and potted green plants, surrounded by bare brick walls at Long's eateries, sipping white wine with their quiche, watching their numbers grow.

What parking lots and development had been to the business of the older Washington, bars, restaurants and small-time real estate deals were to Long and his friends.

"It was this younger group that was willing to get active in the last political campaign. Nobody ever counted on them having any money," Long said. "Marion was a natural candidate. He was the youngest. He was the most dynamic. He was turned in. He'd been a customer in many of these places."

Stuart Long has no doubt that Washington will boom in the next decade. "What I've been preaching is that if you can't make money in this city in the next 10 years, you weren't meant to make money," he said.

And he also has no doubt that the racial population of this city will shift, with blacks shrinking from the current 70 percent to 55 or 60.

"Today, it would be absurd for a white politician to yearn for the mayor's office. I don't think it would be absurd 12 years from now. It would still be a long shot, but it wouldn't be absurd," Long said.

But he is not campaigning for white control of the city, Long said. He's not afraid of blacks remaining in power: "I've always taken the approach that we're a minority in the city. We have to accept that. I've never gone around with a chip on my shoulder. I've never gone around as being white first. I've never had that paranoia that a lot of people have."