He looks younger than his years, his barely lined face dominated by sparkling silver-framed eyeglasses creating a professional grace. Followers walk fast to keep up with his rapid, rolling stride. From a distance - the vantage point from which most have seen him - he is the reserved and competent leader of the fledgling City Council.

Sterling Tucker, 54, quietly responded to a comparison of him to a tense, tight-muscled track sprinter. "No, I never ran track, but I'm fast," said the lean and energetic Tucker. And that is the way he is running for mayor - hard and fast.

During a recent week of campaigning Coucil Chairman Tucker crisscrossed the city visiting a Georgetown disco fund-raiser, spoke to a small group at Anacostia Baptist Church, defended his council record before a hostile night high school class in Shaw and was amicably received by his Alpha Phi Alpha fraternity brothers in an upper Northwest church.

His pace matches his intense concern about maintaining his lead - shown in months-old polls - over his major rivals for the mayor's seat, countil member Marion Barry and Mayor Walter E. Washington.

Tucker is credited with steering the infant City Council through its stormy beginnings four years ago to the older, more experienced body it is seen as today.

In the process, Tucker gradually has taken on the image of a bureaucratic administrator loftily removed from the visceral issues that people vote on. Years ago, he was seen as the feisty Urban League director, pushing for expanded job opportunities in a de facto segregated Washington. Today, he is perceived as the moderate boardroom mediator, soothing the divergent personalities of the City Council in easing the path to pass legislation - a distant, but efficient manager.

"I'm seen as removed" from day-to-day issues, Tucker acknowledged, "but if there is a liability (in that image) there is also an asset. People know that I am (a) competent" administrator, he added.

"People know it is logical for me to move from the chairmanship of the council tothe mayor's office," he continued. "I'm seen in that role."

His campaign workers, supporters and friends say that the perception of Tucker as a formal and intellectual politician could hurt him among Washington's low and moderate income voters. But his base among the city's middle and upper income groups remains strong, they say.

"He is essentially reserved, shy and bashful," said one of his campaign aides, " which can be interpreted by some people as aloof and snobbish." Another campaign staffer said Tucker "is not a bounding extrovert and has a professional image. That can't help him."

"I don't think I have a negative image (among low income earners)," Tucker said, "but I think some of my people think I do."

A tough, wily politician who reveals little about his campaign that could be interpreted as unflattering, Tucker maintains that a poll he has had done for himself "shows that I have support among all groups."

Through oblique conversations, however, his campaign workers - many of them wary of prying reporters - indicate their candidate's strengths are in the liberal white and middle income black areas of the city. Barry has backers in those groups also but Tucker seems to have begun with more support.

In a campaign where no clear issues separate the three front-running candidates, Tucker said it is "a clear statement of fact" that he and Barry could split the same constituency in the primary, propelling Mayor Washington into a victory by a pluralistic margin.

"But you can't live nervously," he added. "I live with creative anxiety which keeps me on my toes."

The maor "issue" Tucker emphasizes in his campaign speeches is his personal involvement in the city's affairs over the past two decades, constantly reminding his audiences that he has been here for a long time. Besides his Urban League activities, Tucker tells his audiences that he had a prominent role in shaping the home rule charter as chairman of the Metropolitan Coalition for D.C. Self-Determination.

The coalition lobbied for home rule and was closely tied to Del. Walter E. Fauntroy (D-D.C.), one of the city's most popular Democratic politicians.

Fauntroy, who is believed to have one of the most effective political orginazations in the city, is actively helping and promoting Tucker's campaign for mayor.

Tucker rarely mentions either Barry or Mayor Washington by name. But in his speeches he accuses Washington of running an inefficient administration that is so unresponsive that people look elsewhere for solutions to their problems.

"People (still) think they should call the Congress to get their trash removed." Tucker told a group of about 60 U.S. Postal Service mailmen. "It ought not be that way today."

As Tucker would down his 15-minute spech, the mailmen began to fidget, scraping their chair legs against the floor and talking in unswhispered conversations with their friends.

It was before such moderate income groups that Tucker seemed to get the poorest response during a recent campaign swing. Later in the week, after speaking to the mailmen he addressed a class of night students at Armstrong Adult Education Center.

After that speech one student, Lee G. Robinson, 25, said of Tucker, "He didn't leave me with any impression."

Two nights before Tucker's talk to the Armstrong students, Douglas Moore, the maverick Democrat who is running for council chairman, had addressed them. Moore told the group that Tucker had "sold out to the Metropolitan Washington Board of Trade) and the city's big landlords."

Tucker walked into the classroom defending himself. Without naming Moore, he said, "My colleague said I didn't support poor people, that I didn't support rent control."

"Well, (Moore) voted against rent control," added Tucker as several students gasped in surprise. Moore said he voted against rent control because the bill was too weak.

Tucker then launched into a teacher's style talk on civic responsibility, exhorting the students to study each candidate's voting records before deciding for whom to vote. But the students, most of whom are in their 20s, grew restless and began raising their hands, several of them vocally interrupted Tucker and demanded that he respond to their questions.

In a response to a series of rapid-fire questions from one student, Tucker answered "Yes" when asked if he would provide better housing for the low and moderate income people of the city. The students broke out into cynical laughter.