The new chairman of the House District Committee paid a call on the new mayor of Washington yesterday, promising to be "an advocate, not an overseer, of District affairs."

After decades in which city officials have trooped up to Capitol Hill to plead for help from an often-skeptical Congress, Rep. Ronald V. Dellums came down to the District Building for what he called a "more than symbolic" visit to Mayor Marion S. Barry's office. "It was important to travel here and meet... on the people's turf," he said.

Dellums and Barry issued no dramatic pronouncements on the issues they discussed yesterday -- which included the city's pension problems, the size of the federal contribution to the D.C. budget, and the eternal debate over a commuter tax -- but both seemed optimistic that a corner had been turned in city-federal relations.

When their 45-minute meeting was over, Dellums voiced admiration for Barry as "one of the most exciting politicians in the county," and Barry said Dellums' visit marked "a new partnership, a new relationship between... the District government and Congress."

Although Dellums was elected to his new post only four days ago, city officials and House colleagues are already predicting that this lean, tall immaculately groomed California Democrat will make his presence felt in D.C. affairs.

Rep. Herbert E. Harris II (D-Va.), a fellow liberal committee member, predicts chairman Dellums will be "active, out front."

Rep. Stewart B. McKinney (R-Conn.), the ranking minority member, sees Dellums turning the District committee into an "urban showcase," a prospect that, needless to say, conservative House members do not relish.

Dellums is one of a very few members of Congress who not only live in the city, but send their children to its public schools. He and his wife Leola (Roscoe) have two children in junior high school and one in high school here. They live in Northwest Washington, west of Rock Creek Park of Military Road.

With eight years of congressional seasoning behind him, the former Berkeley social worker, street activist and city councilman brings to the committee a zeal for the work shared by few of his colleagues.

"These guys aren't exactly falling over themselves to come aboard," said Dellums on Wednesday, wondering aloud whether the committee's size should be reduced to make it easier to get a quorum.

The 43-year-old Dellums ascends to a position most recently occupied by convicted Rep. Charles C. Diggs Jr. (D-Mich.), who often seemed more interested in Africa than Anacostia, and before that by John McMillan (D-S.C.; now retired) who struggled to maintain what critics saw as the colonial status-quo here while preserving tobacco support prices back home.

Dellums' interest in local affairs dates back to his first term in the House, when, after the antiwar May Day protests of 1971, he sued the city on behalf of 1,200 arrested protesters.

When George Washington University announced plans to abandon sponsorship of its Urban Law Institute, a training ground for black lawyers, he denounced the decision as "ractst." When Dellums was arrested in the May Day demonstrations, he said one policeman had struck him with a club. "They didn't give a damn about the fact that I was a congressman -- I'm a nigger," he explained.

When televising of House sessions was debated last year, Dellums implored members to use in-house production crews, denouncing the commercial networks as "white, male dominated."

He won his seat in 1970 despite being singled out for attack by then-vice president Spiro T. Agnew as an "out-and-out radical." Dellums says he does not object to the label. "If being an advocate of peace, justice and humanity toward all human beings is radical, then I'm glad to be called a radical."

By his second term, Dellums was chairman of the Congressional Black Causcus, in which he remains active. But as he begins his fifth term, he is exhibiting that recognized hallmark of political maturity -- a willingness to compromise.

Dellums has softened his determination to push for a commuter tax, for example. At the District Building yesterday, he said he would hold off on that issue if Barry and city officials think other priorities should come first.

One of those other priorities, Dellums has said, could be the D.C. voting rights amendment. And if that amendment is ratified, Delums' name is one of several mentioned as possible "carpetbagger" candidates for a District seat in the U.S. Senate.

But Dellums insisted this week that he has "no aspirations" for a Senate seat from D.C. Even if he did, he added, as chairman of the House District Committee he would "not want to be involved in the politics of the District." Such interference could cost him the support of House colleagues when it came to asking for help on behalf of District legislation, he said.

As for ambitions, Dellums said "I'm not even sure how long I want to stay in Congress."

Part of Dellums uncertainty may spring from the quixotic condition of his 8th Congressional District in California, which includes the University of California at Berkeley, the heavily black inner city of Oakland and the white suburbs of Alameda and Contra Costa counties.

"Ron could be beaten in any election, either by someone who accuses him of being too conservative, or by a conservative who paints him as a radical," said one observer of California politics who sees Dellums as a would-be Senate candidate from the District.

The principal challenge facing the District committee, according to several committee members, is the permanent financing of a Metro rail system. Dellums sees the problem as a chance for Congress "to develop a model system... without having to go on a junket. The president and all of us can show the rest of the nation how to make things work here, whether it is solving unemployment, or building a subway.

Dellums' booming voice and striking coiffure -- the moustache and Afro are streaked with just the right amount of gray -- served him well two years ago as the star of a WRC-TV special, "The Trials and Triumphs of Frederick Douglas."

Dellums and Douglass, the freed slave and celebrated author and orator, have a natural affinity. Both worked as farmhands when they were children, Dellums picking beans, apricots, peas, strawberries and cotton in northern California. Like Douglass, Dellums is known for his ability to speak extemporaneously, and like Douglass he sees himself as a humanist.

One of the House's nattier dressers, Dellums allowed Playboy magazing to dress him for a fashion spread on Congress, admitting "I love clothes."

"At one level in Congress, we are all actors," he said once when he was asked about his avocations as actor and model. "We are so busy playing our roles -- the left wing, the right wing, the Midwesterner, the farmer, the minister... Mayble we could solve problems better if we would break out of those roles. Maybe we could then come to grips with what we have to do."