In the middle of Hill Street Blues, Georgetown basketball and late-night movies, a political commercial. A shiny faucet appears, water dripping from it, and the announcer says: "D.C. government hasn't fixed anything for a long time. Year after year the problems never go away."

A hand appears to turn off the faucet. And then, there in living color is John Wilson, Ward 2 Democratic councilman and candidate for mayor. He introduces himself and says, "With your help I can do the job right."

Wilson's leaky faucet is the star so far of the earliest crop of commercials ever to appear in a District election. The Wilson spot is the only television ad in a slew of radio commercials from four candidates for mayor: Wilson, physician Morris Harper, and at-large Democratic City Council members Betty Ann Kane and John Ray.

The ads all attack the incumbent, Marion Barry, for "waste," "bad management" and "debts," as it is put in the Wilson commercial. But this early round of advertising is not so much aimed at Barry as it is a competition between lesser known candidates to see which of them can move out of the pack into position to run as a major candidate once the campaign gets into gear.

Spending money this way so early is a gamble, but these contenders see it as a risk necessary to gain their footing for the race to come. For the candidate whose name recognition goes up, the bet will have paid off.

At the same time, however, the early advertising foreshadows the content of this year's mayoral debate. Although the mayor begins with the advantage of incumbency and with strong support from the business community, the commercials' common theme makes it clear that other candidates believe he can be challenged on the issue of how well he has managed the city's day-to-day operations. The opportunity the challengers see is that Barry has apparently begun his campaign with unusually low popular support for an incumbent, according to early polls.

The leaky faucet in Wilson's commercial is a clear allusion to the confusion in Barry's administration over water bills. Kane's commericals speak directly to the mayor, saying she will get out of the District Building and not offer excuses for poor performance. Even Ray's jingle, in which a "man makes his way to meet and hear and listen," broadly hints that the incumbent is out of touch.

Barry declines to comment on the commercials' view of his tenure as mayor.

The immediate challenge for Kane, Ray, Wilson and Harper is to establish themselves in voters' minds as serious contenders, and to gain some ground on the two contenders leading so far in the polls and dominating political strategies in all camps: Barry and former Carter cabinet member Patricia Roberts Harris. These polls, however, are extremely early ones, and the campaign is yet to begin in earnest.

"I've got to dispel all questions about whether I'm a serious candidate for mayor," says Wilson. "People see the commercial and their attitude changes. They say: 'He must be serious to be spending all that money.' That's why spending the money early is no mistake. If the ads work I'll get more money, too. If people decide you might win, they'll give you some money."

Wilson so far has raised about $180,000 and has spent about $31,000 of it on ads: $25,000 for television time between Feb. 15 and Feb. 23, another $4,000 for the production of his commercial and $2,800 to his political consultant at Rothstein/Buckley who handled the commercial.

John Ray has paid approximately $90,000 to Bailey-Deardourff & Associates Inc., a political consulting firm, to handle his radio commercials, get a song written to accompany them, have signs placed on the sides of buses and put his posters on lampposts and trees.

That investment is more than half of the $171,000 that Ray has spent on his campaign. His commercials played about 500 times on 10 radio stations between Jan. 22 and Feb. 5, but their impact so far appears less than he had hoped.

"In terms of the recent polls taken, I'm not really pleased," says Ray, who got 6 to 9 percent of the vote in those surveys. "I'm pleased in terms of what I hear about the commercials. People were talking about them . . . . What I don't know is how effective they were in helping the campaign. We are going to take our own poll in May, and that should show whether the ads did anything for us."

Ray's political consultant at Bailey-Deardourff, Dan Pero, says he thinks the ads worked to improve the candidate's name recognition simply because they sparked talk.

"We've got to let people know that John is out there," Pero said. "I think we accomplished that."

While Wilson took to television and Ray to radio with a jingle, Kane built her commercials around testimonials from voters on her willingness to work for people who need government help and on her ability to make the government function properly.

One of her two commercials, which have been running since March 11 and will continue until Thursday, begins with a woman saying: "There's the next mayor, there, Betty Ann Kane." A male voice enters: "I find her to be the most intelligent and effective individual in high public office in the District."

The impact of Kane's ads is not yet known, but her campaign has been gaining in financial support after a very slow start and the commercials could add to her momentum.

"We want people to know that she is a serious candidate," says Deno Seder, of Deno Seder Productions, the company handling Kane's advertising. "We want people to appreciate her unique differences from the others who want to run . . . . Voters are skeptical of what politicians say, so we let voters talk about Betty Ann."

The fourth candidate already running ads is Morris Harper, a physician who is making his debut in city politics as a candidate for mayor. Harper says he has spent $6,000 of the $23,000 he has collected to place 60-second commercials on five stations. The ads feature only Harper's voice.

"My name is Morris Harper," he begins, "and I am a Democratic candidate for the office of mayor in the District of Columbia . . . we need leadership, new ideas, creativity and some long-range planning for this city. With your support and your vote we can and we will turn this city around and begin to make it work for all of our people."

In general, all the commercials seem to aim at a broad audience rather than seeking support from specific groups of voters, as candidates are more likely to do in the later stages of the campaign.

Harper, Kane and Ray picked many of the same stations to air their ads: WGMS (classical music); WTOP (all-news and Bullets and Capitals games); and WHUR (sophisticated black music).

In addition, Ray and Kane both bought time on WRC (news/talk) and WMAL (music, news and radio personalities). Those stations, according to advertising executives, are targeted largely at Northwest Washington's black and white middle class, a group that makes up about half of the city's voters.

Where Kane and Ray differed was in their approach to the rest of the city. Kane chose WYCB (gospel); WOL (popular soul music) and WEAM (big band music). Ray bought ads on WASH (soft rock); WGAY (easy listening music); WPKX (country) and WMZQ (light rock) and WKYS (Disco and soul).

"That's a crazy buy," said one ad executive of Ray's choice of stations. "He spent his money to reach young whites in the suburbs." Pero, Ray's media consultant, characterizes the choice of stations for the commercials as a "wide spectrum." He said the campaign is trying to reach all of the voters and opinion makers.

Kane's choice of stations, particularly WOL and WYCB, were considered good buys by advertising executives and other campaigners who say she is trying to get her name and a positive image into working-class black homes, where she may not have been considered a possible candidate for mayor. Her radio strategy closely followed Wilson's approach to selecting television stations.

Wilson's 36 ads played on soap operas, game shows, and late-night movies on all five commercial stations in the city, with only 10 in prime time.

"Some people say it's a waste to have ads on TV now," says Wilson. "It goes to Maryland and Virginia and all that. That's right, but let me tell you I did TV last time in my council race and everyone said I was crazy. I had them on late-night movies, which I think is the prime entertainment for poor people in this town. When I went out after those commercials into low-income areas I was mobbed, mobbed."

In addition to Wilson, Ray, Kane, Harper, Barry and Harris, council member Charlene Drew Jarvis (D-Ward 4), Denis Sobrin, publisher of a sexually oriented newspaper, and Richard Jackson have filed as candidates for the Democratic primary for mayor. Barry and Harris have said they will begin advertising their campaigns in midsummer. Jarvis said yesterday she will begin a $10,000 to $15,000 radio advertising campaign in April.

Barry and Harris have yet to announce. Harris had scheduled her announcement for yesterday, but changed the date to April 3.