SHE HAD CERTAINLY SPENT ENOUGH TIME around politicians to know better, including 10 years in the House, but Barbara Mikulski regarded the United States Senate as something different. The Polish grocer's daughter wondered half-seriously whether senators "powder their wigs in the morning" and described the first meeting of the Democratic caucus she attended in January in almost reverential tones. There she sat, enraptured, watching as Sens. Ernest F. Hollings of South Carolina and Lloyd Bentsen of Texas debated trade policy and quoted from "The Federalist Papers."

"For there to be both intellectual substance and wit, I thought, you know, 'I think I'm going to have a good time,' " Mikulski recalls. "This is my kind of crowd."

It took less than four weeks for Mikulski to be reminded that her new colleagues were perhaps not so different from the ward heelers she knew back in East Baltimore. The reminder came not in the halls of Congress but at a banquet room of a downtown hotel where 650 Washington bigwigs, including senators, big businessmen, Cabinet members, Supreme Court justices and Vice President Bush, were getting together for the annual rites of a male institution called the Alfalfa Club.

There were skits, spoofs and lots of jokes about Iran and Ollie North. Toward the end of the night, New Mexico Sen. Pete Domenici, normally a bland Republican, got up to deliver the campaign speech of a presidential candidate on the Alfalfa Ticket. "I'm blessed with the talent of . . . whipping the electorate to a frenzy," he proclaimed. "Just like the singer Tom Jones, women often throw their panties at me when I speak. It happened again just yesterday. I just don't know what got into Senator Mikulski."

Mikulski first heard of the remark the next afternoon when an aide called to say a reporter was seeking her comment. "I was livid. Livid," Mikulski says. In fact, it was a crisis of sorts for the freshman senator from Maryland, her first public test. Should she laugh it off and hope the subject would fade away or should she confront the issue? Mikulski followed her instincts. "I think it's outrageous and I find it insulting," she said. "I have other responses, but that's the one for public dissemination."

Vintage Mikulski. Or was it?

This was, after all, the woman who organized a powerless neighborhood and stopped a highway, who became a voice for forgotten ethnics, who loudly and brashly proclaimed the right of women to participate fully in the political process, who once called for Defense Secretary Caspar Weinberger's resignation, who bragged about "slam-dunking" her opponent in the last election. And in those street-fighter days, Mikulski would have been slow to forgive and unlikely to forget. Aggrieved and angry, she would have seen the Senate as a hostile environment. But people who remembered that Mikulski were in for a surprise.

When Domenici called the next morning to apologize, Mikulski was conciliatory. Together, they drafted a statement in which a contrite Domenici said he "never intended to be offensive." For her part, Mikulski said the matter was closed. Two months later, on the floor of the Senate, she went out of her way to chat Domenici up and praise him for an article he wrote on the homeless. She wanted him to know there were no hard feelings, that she didn't have a chip on her shoulder.

Barbara Mikulski wanted to join the club.

Her colleagues, some of whom had viewed her arrival as the second coming of Bella Abzug, were watching closely -- and were impressed. "She understands it's still an all-boys club, and she's going to be a player," said Sen. Dennis DeConcini (D-Ariz.). "She already is."

That there would be surprise about the skillful way Mikulski handled the Alfalfa Club incident was probably inevitable. Throughout her two decades in politics, people have underestimated her and her ability to adapt. Now she's adapting again, offering her fellow senators a different though shrewdly appropriate Mikulski -- more accommodating, more cautious, acutely aware of the need to convey a more serious and "senatorial" image.

"I find her style more relaxed, good-natured, a little less shrill and harsh," says Linda Dorian, executive director of Business and Professional Women/USA, the oldest professional women's organization in the country. "She seems to be more comfortable with herself, her position, her power."

There was a time when Barbara Mikulski didn't much care how people perceived her. She was what she was: a stocky, 4-foot-11, rough-edged East Baltimore politician once described as having "the heft of a stevedore and a voice to match." But when she decided to run for the Senate a year and a half ago, Mikulski came to the realization that at the age of 48 she would have to change her looks and combative style if she hoped to win. She lost weight through rigorous dieting and morning workouts on an exercise bike. Once a frumpy dresser whose taste ran to Catholic-girls'-school-style blazers and blouses, she began wearing Ultrasuede suits and carefully tailored dresses picked out with the help of a fashion adviser. Her hair is styled at Elizabeth Arden in Washington, thank you, and she seems to wear a different pair of shoes every day. "I used to think Ferragamo was a restaurant in Little Italy," she says.

When she defeated Republican Linda Chavez with 61 percent of the vote, she was not just another freshman senator but a national celebrity. Mikulski was the first Democratic woman to win a seat in the Senate in her own right, and the party's congressional leadership showed her off by temporarily assigning Mikulski to Harry Truman's old seat on the Senate floor. And she presented a sharp contrast to the only other woman in the Senate, Nancy Landon Kassebaum (R-Kan.), a dignified-looking millionaire businesswoman who came to the Senate nearly a decade ago largely on the strength of a prominent family name (her father is former governor and presidential candidate Alf Landon of Kansas). Mikulski, on the other hand, was a striking symbol that it's possible for someone who is not male, wealthy or possessed of good looks, who is fiercely outspoken, to take a place among the wealthy white males who traditionally dominate the Senate. Ms. magazine named her a "Woman of the Year."

During the campaign, Mikulski was criticized, first by Rep. Michael Barnes, one of her primary opponents, and then by Chavez, as lacking the grace and polish to make it in the Senate. Chavez took it a step further, branding Mikulski as a "San Francisco-style Democrat" and an "anti-male feminist," undesirable credentials for getting along in the world's most exclusive men's club. But Mikulski has adapted quickly to the Senate's rarefied atmosphere -- the slower pace, the more deferential tones, the little courtesies and tugs at the elbow that grease the wheels and cement relationships. With timely help from her friend Sen. Paul Sarbanes (D-Md.) and Majority Leader Robert C. Byrd (D-W. Va.), she landed four of the best committee assignments of any freshman. And though she remains the favorite of the National Organization for Women and other women's groups, she no longer feels obliged to get out in front of every women's issue.

Despite these changes, Mikulski insists, she still has the soul of a street organizer. "Nobody would ever use the term mellow to describe me," she says. "I'm not caffeine-free, that's for sure." But her evolution underscores what those who have known her best have seen all along, a master political strategist whose ability always to rise to the next challenge has been consistently underrated. "If anything has changed, public attitudes about her have changed," says Ann Lewis, a longtime friend and national director of Americans for Democratic Action. BEYOND THE GLEAMING GLASS ROOF OF THE Baltimore Aquarium and the graceful concrete curves of the Inner Harbor, East Baltimore looms like a defiant, enduring monument to ethnic America. Little Italy, with its zigzagging cobblestone streets, serves as the gateway to this balkanized collection of diverse and quirky neighborhoods. Farther on, past the bustling Italian restaurants and old warehouses, are block after block of brick row houses with scrubbed marble steps and proud Catholic churches whose pews still brim on Sundays. These are the Polish neighborhoods -- Fells Point, Canton and High- landtown -- where immigrant steelworkers and laborers and their families flocked at the turn of the century. Interspersed are enclaves of Greeks, Lithuanians and Ukrainians who give East Baltimore its rich ethnic flavor. Invisible boundaries, lines drawn over decades by intense ethnic and political rivalries, separate these neighborhoods.

Politics as traditionally practiced here is also a throwback to another era, with ward bosses and neighborhood clubs, "walk-around money" for Election Day workers and vestiges of once-powerful Italian and Polish political machines. It was Barbara Mikulski's triumph to win the loyalty of this deeply conservative area while remaining a liberal. She did it with a classic urban populist issue -- organizing opposition to a highway proposed in the 1960s that would have destroyed much of East Baltimore. In the process, she also managed to oppose the new mayor of Baltimore, William Donald Schaefer, and eventually win him over, marking the beginning of a long political relationship. Launched by the highway issue, she bucked the local Democratic organization and won her first term on the Baltimore City Council. By the time she ran for reelection, she had the organization's support.

William and Christine Eleanor Mikulski, second-generation Polish Americans, ran a tiny grocery store called Willy's Market across the street from their home in Highlandtown. Barbara, the eldest of their three daughters, attended Catholic girls' schools for 16 years and lived at home with her family until she was 27.

Even as a little girl, her mother recalls, Barbara showed a special talent. While other kids were more athletic and agile than the klutzy, chubby Barbara, she had an uncanny ability to control situations. Tired of skinning her knees trying to jump rope "double dutch," Barbara coaxed her little cousins and friends into taking part in plays and shows in her parents' garage, shows in which she served as playwright, producer and director.

Mikulski considered becoming a nun but concluded she was too rebellious to accept the discipline of an order. Instead, she trained as a social worker at Mount St. Agnes College in Baltimore and the University of Maryland and went to work for Associated Catholic Charities and then the Baltimore Department of Social Services. Practicing a philosophy of what she calls "tough love," a sympathetic but hard-nosed approach to welfare clients and drug addicts, she urged them to set realistic goals and then relentlessly pushed them to succeed.

By 1966, Mikulski was an energetic assistant chief of community organizing for the city social services department, working on a plan to decentralize welfare programs. That year, she met Sister Mary Elizabeth, who had left the Little Sisters of the Poor to establish her own hospitality house and school in a poor black area of Baltimore. The nun was the consummate outsider, a tough and assertive advocate of non-violent change and empowerment of the poor who would be a major force in shaping Mikulski's political philosophy.

"She saw her role as to either meet the needs {of the poor} or shake the hell out of the bureaucracy," Mikulski recalls. "I would go over there every Wednesday. I was on my way to becoming a real hotshot administrator, an up-and-comer in social services. When I went over there, she said, 'Well, Barbara, you're out there changing the system. Here's the system I want changed.' "

Sister Mary Elizabeth taught Mikulski, a bureaucrat herself, to be suspicious of bureaucracies and to distrust new programs not grounded in practical experience. She played another role, as well, introducing Mikulski to Dorothy Day, the co-founder of the Catholic Worker Movement, and other Catholic social activists and thinkers.

As a social worker, Mikulski gradually was drawn to the civil rights movement and a fight over efforts to desegregate Baltimore neighborhoods. In 1968, while she was attending graduate school and debating whether to remain in social work, a fellow student told her about the battle brewing over the proposed highway.

It was to be the perfect outlet for her defiant personality and talents as an organizer. The fight pitted a neighborhood organization, the Southeast Council Against the Road (SCAR), against an entrenched Democratic political organization at city hall that supported the highway project. The highway fight eventually led to the city council. "For a woman, with no previous political experience, to run out there was a tremendous accomplishment," says Peter N. Marudas, a Sarbanes political adviser.

By the time she reached the council, she had gained national attention for an article in The New York Times in September 1970 in which she wrote that ethnic America was "forgotten and forlorn," a target of media stereotypes and falsely branded as racist by phony, "elitist" liberals. She confirmed her liberal credentials, though, by working on George McGovern's ill-fated 1972 presidential campaign, and made some important contacts in the national party organization that led to her appointment as chairman of the commission that rewrote the rules on delegate selection.

Clearly, Mikulski had ambitions that went beyond the boundaries of Baltimore, and she went about fulfilling them with the same methodical sense that she displayed in the garage theatrics of her Highlandtown childhood. In 1974, she challenged Charles Mathias, Maryland's virtually unbeatable liberal Republican senator, in what seemed an almost foolhardy move. To Mikulski, it made perfect sense. As a newcomer to politics, she had nothing to lose in running against Mathias and plenty to gain in terms of exposure. She ended up with 43 percent of the vote, a respectable showing that gave her recognition throughout the state -- an advantage her Senate opponents would typically underestimate when she ran for the seat 12 years later.

In 1976 Sarbanes gave up his 3rd District House seat encompassing part of Baltimore and some of its suburbs for his own run at the Senate. It was the opportunity Mikulski was waiting for, but she also realized that the persona that played among the row houses of Highlandtown might not work in Catonsville or on Capitol Hill. She took a hard look at herself and concluded something had to be done about her appearance. Once a Size 20, Mikulski shed 50 pounds and made her diet a running joke during the campaign.

Rumors of strident feminism had preceded her to the House, but she displayed considerable shrewdness in choosing committee assignments and issues that related directly to her district. During 10 years in the House, Mikulski racked up a liberal, staunchly pro-labor voting record. She was also a prime mover behind the 1984 Child Abuse Act and a major spokesman for the Equal Rights Amendment, and helped found the Congressional Women's Caucus.

If her abrasiveness did not always manifest itself publicly, it still got her in trouble with the people who worked the closest with her -- her staff. By many accounts she was demanding, always in a hurry and insistent that staff members get to the "bottom line," even as they worried that she was glossing over issues. The one episode that proved most politically damaging to Mikulski -- and haunted her through last year's election -- was her decision in early 1981 to hire Teresa Mary Brennan, an Australian feminist with some unorthodox ideas for promoting home-based businesses for women.

Mikulski met Brennan at the United Nations Women's Conference in Denmark in the fall of 1980 and almost immediately offered her a part-time job. According to news accounts at the time, Mikulski intended to use Brennan's philosophy as a "blueprint" for her congressional work. But others on Mikulski's staff thought Brennan and her ideas were off the wall. Some described her philosophy as "fascist feminist," "Marxist" and "anti-male." At least three staff members quit to protest Brennan's ideas and her growing influence over Mikulski. Before Brennan got settled, she spent several weeks living at Mikulski's home in Baltimore, and rumors began to circulate about Mikulski's sexuality and the nature of her relationship with Brennan. About four months later, Brennan left the staff, but by that time the issue had become a major controversy that Mikulski later conceded "almost destroyed my career." She has denied that there was a sexual relationship with Brennan.

While Mikulski says she enjoyed life in the House, she wanted to play in a bigger game. She began considering the biggest risk of her political life -- another run for the Senate. Her early political soundings throughout Maryland, however, turned up little in the way of firm support or pledges of financial help. Then-Gov. Harry Hughes was widely considered the early favorite for the Democratic nomination. And while Mikulski was better known statewide than Barnes, Barnes was regarded as a stronger candidate because of a national reputation for his foreign policy expertise.

The turning point came in the spring of 1985 at a meeting with some key advisers, including Robert Shrum, a campaign consultant, at a restaurant on Capitol Hill. Over dinner, Shrum posed a difficult question: Could Mikulski survive emotionally if she were to give up her House seat and then lose the race for the Senate? "You have to recognize," he said, "that you can lose everything." Mikulski said she was prepared for that possibility. Then Shrum raised another delicate issue: Mikulski's appearance and image. To run successfully statewide, Shrum told her, she would have to smooth some of the rough edges without tampering with the essential Mikulski. "You want to round out and soften Mikulski, but not change Barbara," he told the group.

Lillian Brown, a makeup adviser to presidential candidates, showed Mikulski how to use low-gloss makeup to give her face less of a pie shape on TV. Mikulski replaced her old, dark-framed glasses with a pair of rimless, glareproof bifocals. She experimented with different-color dresses and varying hemlines so she wouldn't look dumpy. And she learned how to sit properly and take advantage of camera angles to enhance her looks on television.

All these steps, Mikulski says, came naturally. "When I hit 50, I took a little inventory, and I knew that whether it was going into this campaign or hitting 50, I was just going to be a little bit more pampered. I was ready to go into what I'll call Cajun clothing. I was ready for more spice." PRESIDENT REAGAN WAS COMING TO GIVE HIS State of the Union address, and the House chamber was packed. Mikulski, in the same cranberry Ultrasuede dress and vest she wore during her first televised debate with Chavez, stood among a cluster of 14 senators assigned to greet and escort the president into the chamber. As he entered the chamber, Reagan paid little attention to Mikulski, lost among more prominent figures including Byrd and Minority Leader Bob Dole (R-Kan.), until she stepped forward, stuck out her hand and said, "Mr. President, I'm that new Democratic senator from Maryland."

"Yes, I know you are," said Reagan, who had campaigned vigorously in Maryland for Chavez, one of his former White House aides.

"You know," she persisted, "I'm the one you said would go the way of the Edsel, the hula hoop and the asparagus diet. Mr. President, I'm on the asparagus diet."

Mikulski was in a playful and slightly vindictive mood that night after one of the more bitter campaigns in recent Maryland history and after what she felt was some bad-mouthing by her House colleagues. "That's a strut, you know," she says in recalling her return to the House that night. "I guess it's like if you win the World Series and you walk out on the field."

It was a rare display of bravado by Mikulski during her early days in the Senate. For the most part, she has gained acceptance not through aggressiveness, as some had predicted, but through sophisticated political maneuvering. Anyone who doubted her skills at the subtler arts of politics need only look at how she nabbed a seat on the Appropriations Committee, the rarest of plums for a freshman. She launched the effort only two days after her election, ensconcing herself with Sarbanes in his Baltimore office, poring over committee assignment lists to pinpoint key senators to be lobbied and working out precisely what she would and wouldn't say in lining up support.

"We decided to go very hard for Appropriations and not give people a maybe-here, a maybe-there kind of approach," Sarbanes says. "You've got to go all out for it or they can move you around."

Mikulski ended up with not just Appropriations, the "financial AWACS plane," as she describes it, with oversight of every aspect of government spending, but Environment and Public Works, with jurisdiction over road and bridge construction, Labor and Human Resources, which handles most major welfare reform legislation, and Small Business. In all, Mikulski has 12 subcommittees, a full plate that forces her to pick and choose carefully among the issues she gets involved in.

Mikulski is in a prime position to do her state a lot of good. She already has pushed through amendments to a fiscal 1987 supplemental spending bill that will help Maryland: money for the Beltsville Agricultural Research Center and Maryland's oyster beds; instructions to shake loose $24 million in Maryland urban mass transit funds that have been held up by the administration; and language preventing the Federal Aviation Administration from closing a weather station at an airport near Salisbury. This is mundane stuff, but it counts for a lot back home.

During the primary, Mikulski was stung by Barnes' contention that in all her time in the House, she never rose to chair an important subcommittee or pushed through a major piece of legislation. From the day she was sworn in, Mikulski has sought to preempt that kind of criticism.

She pinpointed a major hole in the Reagan administration's proposal for catastrophic health care insurance and introduced a "spousal impoverishment bill" to provide financial relief to families with members in long-term nursing homes. Mikulski had more than a passing acquaintance with this problem. Her 78-year-old father suffers from Alzheimer's disease and is a patient at a nursing home outside Baltimore.

Mikulski's arrival in the Senate has coincided with a decline in neoconservatism and the restoration of a somewhat retooled liberal agenda. The emphasis today is on workfare and other ways to diminish dependence on Aid to Families with Dependent Children. Mikulski, the Senate's only former social worker, is comfortable with this approach because it coincides with her "tough love" notions of dealing with the poor and providing training for the unemployed that will lead to permanent jobs.

As she immerses herself in such issues, she is also demonstrating a vastly increased sensitivity to the nuances of publicity -- and her own image. When a news conference she was giving with Sen. Edward M. Kennedy to discuss a new bill for increased funds for AIDS research drew a large turnout of network camera crews and reporters, Mikulski and her staff were faced with a problem -- her height. While the network camera crews set up for the press conference, Mikulski nervously paced back and forth behind the lectern. She summoned her press secretary, Jim Abbott, from across the room in the Dirksen Senate Office Building. The two surveyed the scene and then nodded in agreement. When Kennedy finished his remarks and introduced Mikulski, Abbott deftly slid a metal suitcase behind the lectern and Mikulski climbed aboard. It wasn't the most dignified moment. But as Abbott warned Mikulski earlier, "If you don't get up on the suitcase, the networks will get a sound bite, but that's about all."

Mikulski has never been a familiar face on the Washington cocktail circuit. For the past decade, she has commuted here from her home in Fells Point, a waterfront neighborhood close to High- landtown that is gradually becoming gentrified. Once these neighborhoods were an integral part of her image, but in the Senate Mikulski seems increasingly self-conscious about not only her own image, but that of her home town. She initially balked at a request to pose for a photograph for this story at a coffee shop and neighborhood hangout in Fells Point where she has long been a regular.

According to Abbott, Mikulski feared such a photograph would somehow reinforce old stereotypes of East Baltimore by depicting her rubbing elbows with gap-toothed truck drivers. It was a peculiar concern for a politician who made a career out of identifying with hard hats, steelworkers and blue-collar laborers.

"What we find in our neighborhood, and it's a little frustrating, we're continually stereotyped and we're treated as something chic, as something real quaint to come to, and it's just about every story that is done," Mikulski said later. "It's almost like a Smithsonian scouting expedition. 'Oh, let's go see the quaint ethnics. Isn't this so cute.' I live in a real neighborhood, with real people who raise real families." She eventually agreed to pose -- but not in Fells Point. MIKULSKI SEEMED UNUSUALLY STIFF AND ILL at ease as she entered the wood-paneled Wicomico County Board room in Salisbury last February. If the dozen Eastern Shore officials there were expecting a joke-cracking, colorful East Baltimore pol, the one who victoriously punched the air election night, they were wrong.

The burghers of Wicomico County -- Democrats, but conservative ones -- voted for Chavez over Mikulski in the general election. Mikulski was there to convince them that the rough-hewn, elbows-out feminist they had worried about was really concerned about their problems. The junior senator from Maryland was all business this day, impatient with small talk and annoyed by the small knot of local TV and radio reporters trailing her. "I want to be the senator not only from Maryland," she told the meeting. "I want to be the senator for Maryland." It sounded hokey, but everyone nodded appreciatively.

Mikulski listened carefully to the officials for more than an hour and frequently scribbled detailed notes on a yellow legal pad. When she addressed board member Betty K. Garner as "councilwoman," Henry S. Parker, the amiable chairman of the board, interrupted, "We're just good ol' Eastern Shore people, and we want you to call us by our first names."

"We all work hard to get those titles -- Henry," she replied.

Long before she arrived for the meeting, Mikulski had begun the wooing process. She knew the county was in a panic over the FAA's plan to close the weather service station at the county airport, and so she had written to Donald Engen, the FAA administrator, urging him to reconsider. She promised to carry the fight to the Appropriations Committee -- a promise that months later would win a reprieve for the weather station. As the meeting wore on, it became clear Mikulski had begun to break through.

Edward J. Kremer, an influential banker and chairman of the airport commission, cast a critical eye on Mikulski that morning and pronounced his approval. "I've watched her on TV and everything," said Kremer. "Her style is a little different, but I like it."

This, then, is the new Mikulski, trying to win over constituencies she never would have had to bother with before, though somewhat ill at ease doing it. This is what it takes to be a U.S. senator and, more important, to stay a senator.

For much of her life Mikulski has operated as something of an outsider, campaigning against the system, even as she was part of it. For all those who had anticipated the spectacle of Barbara Mikulski taking on the Senate, her first months have been a surprise. Like so many before them, they had misread her, underestimated her political skill, her capacity for change. Chances are it's not going to happen again. ::

Eric Pianin covers the Washington-area congressional delegation for The Post's Metro staff.

Mikulski, for her part, tries hard to stay in touch. Above, she kibitzes with customers at a diner in Baltimore's Little Italy.