A small group of doctors and dentists gathered with great ceremony on the steps of the District Building in the mid-morning humidity one day recently to make a pronouncement: They said they were the vanguard of a group of 174 physicians and dentists who are supporting City Council Chairman Sterling Tucker for mayor.

It was an event that, until now, drew the attention of virtually no one, except for a few Tucker campaign aides, including one who taped the statement. Passersby on E. Street kept right on walking.

When the group's spokeswoman, Dr. Bette Catoe, finished the world why Tucker is a "solid, time-tested winner" and how the doctors and dentists plan to raise $50,000 for his single reporter covering the event when he was asked by name if he had any questions.

Although the doctors and physicians were nearly left to talk among themselves, the event was a prime example of the way that Tucker and his chief rivals in the Sept. 12 Democratic mayoral primary, Mayor Walter E. Washington and Council member Marion Barry, are trying to show the voters that they have diverse support for their candidacies.

Like professional sports teams announcing the signing of a prized draft choice, all three candidates have staged press conferences to announce support from various labor unions and try to upstage each others' endorsements.

Some of the endorsements start with a few individuals who support one of the candidates and then recruit more of their colleagues in their profession to give the impression of a groundswell of support. The doctors and dentists said such was the case with their group.

Still to come, the Tucker camp assures, will be Teachers for Tucker, Lawyers for Tucker and Young Adults for Tucker.

There even is a Tots for Tucker, according to campaign spokesman Sherwood Ross. He said this highly visible special interest group is composed of the offspring of adult Tucker workers and can be seen almost daily playing games in the windows of the Tucker campaign headquarters on Seventh Street NW and sometimes even licking envelopes filled with Tucker flyers.

Not to be outdone, Barry's campaign has formed Lawyers for Barry, Restaurateurs for Barry, an arts committee for Barry, Youth for Barry, Architects for Barry, Health Professionals for Barry and Former Student Nonviolent Coordinating Committee Workers for Barry.

The mayor's campaign says it is planning such groups as Lawyers for Washington, Educators for Washington, Youth for Washington and Ministers for Washington, among others.

Once the groups are formed, they often act as unofficial advisers to the candidates on the issues they are knowledgeable about, as fund raisers, and as ad hoc campaigners.

The doctors and dentists for Tucker said they plan to talk about his candidacy with their patients, pay for a full-page newspaper and endorsing his candidacy, distribute flyers in his behalf register voters and raise money.

The doctors and dentists said they are not seeking any particular legislation in the city. They said they support Tucker in the belief that he can run the city's existing health programs better than Mayor Washington.

"He will listen and he is informed," Dr. Catoe said of Tucker. "He's able to corral forces to move programs."

Whatever the benefits, if any, of parading people out at a press onference to endorse a candidate, there also can be more than a few pitfalls.

When Tucker announced the support of 71 ministers last month, two of them said they had no idea that their names were being released as affirmed Tucker supporters. As a result of that experience, the Tucker campaign is double-checking with the doctors and dentists before using their names in a newspaper ad endorsing Tucker.

Stuart J. Long, who owns three Capitol Hill restaurants, formed Barry's restaurateurs' group at the candidate's request.

Long drafted a letter inviting his colleagues in the restaurant business to a $250-a-person Potomac River cruise earlier this month and cited several reasons why they should support Barry.

Among other things, Long's letter said that the extent of the proposed increase in the city's minimum wage for restaurant workers from $2.30 to $3.50 an hour "is ridiculous."

He concluded: "Marion Barry is on our side in this fight. With Marion heading a new administration, we can be assured that our voice will be heard."

Although some letters with those statements were mailed by his campaign aide had the letter redrafted and toned down before it was sent to the restaurants. The new letter simply mentioned the proposed increase in minimum wage without characterizing it or stating where Barry stands on the issue.

The letter concluded with the assertion that "with Marion heading a new administration, Washington, D.C. will have a healthy business atmosphere."

Barry said he does not know how much of an increase in the minimum wage he will support when the proposal comes before the full City Council. The measure is now being considered by a committee.

Whatever Barry's position, the Potomac River fund raiser was a success. Long said $16,000 was raised from more than 60 people who went on the cruise, ate raw oysters, clams, crab claws and other food and chatted with Barry.

"Marion's an old friend of mine from way back," Long said, explaining his involvement in Barry's campaign. "He asked me to help out last winter. He doesn't have the access to the business community that the mayor and Sterling do. I don't either, but I know a lot of small businessmen."

At another fund raiser, Barry unveiled an arts platform, pledging that a Mayor Barry would support neighborhood art centers in which local artists could display their works and the concept of a city museum and study the possibility of a downtown art center.

About 100 artists and campaign supporters paid $10 apiece for a brunch at the Columbia Station restaurant at 1836 Columbia Rd. NW to view the art works and photographs on display and meet Barry.

When Barry made a short speech to the artists, he launched into his standard list of things he says he would do as mayor: provide more jobs, fire the city's housing chief and improve the quality of schools.

Lest Barry forget the group to which he was speaking, a campaign aide quickly scribbled the word ARTS on a piece of paper and waved it alott from the side of the room.

Moments later, Barry assured the crowd, "I'm a strong supporter of the arts."