After four years of managing budget crises and trying with some success to squeeze more efficiency out of the D.C. government bureaucracy, Mayor Marion Barry begins his second term as the undisputed major force in local government--perhaps closer to being a political boss than any official that modern-era Washington has seen.

The 46-year-old Barry, with his graying hair, deepened paunch and natty pin-striped suits, is a far more polished and cautious figure than the social reformer who took office in 1979.

Now, with a strong mandate from the voters and with a new government team in place that includes time-tested loyalists as well as others who stood by Barry during the bleakest periods of his first term, the mayor looks to a peaceful reign and beyond.

He talks in terms of power and wielding it for the greater good of the city. He boasts about his city-wide political organization and compares himself, without using the specific label, to a political boss.

"I think any effective politician has to have a strong organization to survive politically and to govern," Barry said in an interview last week, sitting near a roaring fire in his fifth-floor District Building office.

"Any mayor or senator or governor who does not have a well-oiled, strongly loyal and committed organization working won't be in office very long," Barry said, adding, "I'll never apologize for having a good organization. The stronger it gets the better I like it."

Barry says he plans to be more assertive in pursuing high-priority projects, especially trying to get people off welfare and into jobs. He also says he will spend less time talking to reporters to give himself more time to think and to lower his profile in the local media, even as he campaigns for a more prominent national image.

"I just need time to think more about some decisions," he said. "I'm contemplative about major decisions, but quite frankly sometimes I need just a little more time thinking through decisions."

For nearly half his life, Barry has pursued his passion for politics and community organization. As he approaches age 50, he has begun to consider the limits to what any politician can achieve in a career.

He likes his job, but yens for even higher office--perhaps a federal cabinet appointment--before he retires from public life.

"Obviously I don't intend, even if the public wanted me to be, to be mayor but for so many terms," Barry said.

"In 1984, obviously I'm hopeful that we'll get a Democrat in the White House, and who knows when federal job opportunities will come after that? I like being mayor. I enjoy the opportunity to serve and to help people. It would have to be something awfully attractive that would take me away from being mayor."

At the same time, he says he wonders whether he is missing out on some of the simpler pleasures of life, like spending more time with his young son, Christopher. He says he thinks about having a life at some point "that won't be a public life."

Barry is a complex personality, an aggressive, often boisterous, seemingly irrepressible man who at times seems strangely ill-at-ease or unsure of himself--for example, when he self-consciously wipes away the heavy perspiration that often beads on his brow. He is a brooding figure who shows flashes of humor and playfulness; a shrewd judge of others' strengths and weaknesses who holds his own cards close to the chest and who is said often to be crafty when negotiating.

He is a man with a rough edge--"a diamond in the rough," according to one former aide--who engenders both intense loyalty and deep resentment and fear. Of his political hero, the late Harlem congressman Adam Clayton Powell Jr., a flamboyant and highly controversial figure, Barry says: "He was the kind of person who, in spite of all the odds, became an effective politician."

The image-conscious Barry and his wife, Effi, were hurt by published criticisms of the mayor's private life style during the campaign. Barry complained about those criticisms during the interview, and also said he resents rumors that he somehow has personally profited from his political associations, an accusation the mayor flatly denies.

"There is always an insinuation in the press that there's some hanky-panky going on in my dealings," Barry said. "The people who know me know that I don't need to take a dime from anybody. I'm comfortable with what I make in terms of my income."

The Rev. David H. Eaton, president of the D.C. school board and Barry's pastor at the All Souls Church, said the mayor has "kept his essential humanity" while coping with difficult city financial and management problems. "He brought a sense of stability to District affairs," Eaton said.

Yet Eaton frets that Barry has become obsessed with power politics and at times "comes across as being a hard-nosed politician." In particular, Eaton and other members of the school board are alarmed by a proposal of Barry's transition team to expand the mayor's influence over spending for public education, the principal domain of the school board.

"I think Marion believes an individual mayor can control the process of government," Eaton said. "I disagree with Marion on this . . . . I believe in management and leadership by consensus, which is more difficult."

Today's inaugural festivities, including a lavish ball this evening at the D.C. Convention Center, will be far more regal than the informal people's inaugural that the one-time civil rights activist staged after his first election.

The elite of Washington's business community who once shunned him, the minority businessmen who thrived under his administration, and the labor and civic leaders who came to respect his clout and political skill will be present when Barry is sworn in by Chief Judge Spottswood W. Robinson III of the U.S. Court of Appeals.

Barry's inaugural message this year is likely to be a little shorter on idealism than when he pledged four years ago, in outlining his view of the role of government, that "we will be our brothers' keeper."

Barry has become increasingly concerned about the plight of middle-class residents and businessmen who are being driven from the city by high taxes. And, in the face of declining federal and local revenues, the mayor has begun to preach the gospel of self-reliance and limited expectations.

"That gospel, if it's a gospel, is an imposed gospel," Barry said last week. "I didn't create the lack of resources or the increase in needs for social services and the cutback in the federal government's support."

Courtland V. Cox, who worked with Barry in the Student Non-Violent Coordinating Committee in the mid-1960s and who now is a top aide to the mayor, said Barry's concern about the poor and the elderly hasn't lessened, but that as mayor he now must consider a much broader constituency.

"There's always a difference in being in a position of advocacy and being in a position of power," said Cox.

Barry, who as a young boy chopped cotton by his mother's side in Arkansas and who rose to prominence in Washington as a militant street organizer, cofounder of a self-help organization for the city's down-and-out called Youth Pride Inc., and as president of the school board and a member of the City Council, narrowly was elected mayor in 1978.

Many doubted he had the talent, breadth of experience or the staying power to lead the D.C. government or improve on the record of his predecessor, Walter E. Washington.

Barry got off to a rocky start his first two years in office. He found it far more difficult than he had imagined to assert control over departments that for years had been operated virtually as fiefs of congressional committees. Under the city's old bookkeeping and cash-management system, the mayor had trouble controlling spending, and the longterm debt began to soar.

But gradually his administration imposed much more order in city finances, while at the same time keeping Barry's campaign pledges to boost spending for housing and programs for the elderly, and improving some city services.

Barry won over or wore down many of his critics with the same raw energy and cunning that he exhibited as a SNCC organizer and street activist.

One member of the City Council who has had repeated dealings with Barry describes him as a master at shifting blame for his own policies to others.

"For example, in looking at his fiscal 1984 budget that will be coming over here soon, I know what's going to be in that and it's going to be horrible for the poor," the council member said. "He has promised not to raise taxes or RIF any employes and give a 7 percent pay increase. It's the people without a constituency who will get hurt. Barry will take heat for two or three days, and then the council will take all the heat for the next 45 to 50 days."

Last fall, Barry dazzled his political challengers, including the formidable Patricia Roberts Harris, with a highly efficient campaign organization, an impressive list of endorsements and a record $1.3-million warchest. Barry won the all-important Democratic primary with nearly 60 percent of the vote and then coasted to victory in the general election.

He attributed a large measure of his success to the citywide network of supporters that he and his top political adviser, Ivanhoe Donaldson (now a deputy mayor), carefully nurtured over the years.

Now Barry looms as the preeminent force in local politics. He oversees a $2 billion yearly budget and 40,000 city employes and dispenses millions of dollars in contracts to grateful businessmen, including many minorities. He also exerts considerable influence over the City Council, where usually he can round up an easy majority of the 13 members.

The major shakeup and reorganization he ordered after the election, including the creation of three new deputy mayor positions, will lead to more efficient government and relieve Barry of many day-to-day chores, he insists.

In a move to enhance his national reputation, Barry recently won election to the 30-member board of directors of the National League of Cities. He also has conferred with several Democratic presidential aspirants, including former Vice President Walter F. Mondale.

"There's no way that a mayor of the District of Columbia could ignore national or international affairs , because anything which happens in the world also affects us in the District as a city," said Barry. "My priority is local--my priority is the citizens of the District of Columbia. "But I've got enough time, enough brains and enough tenacity to do all three. And I'm going to do all three."