The prospects for a hotly contested mayoral campaign in the District diminished significantly during the weekend when D.C. City Council Chairman David A. Clarke announced that he will not take on Mayor Marion Barry. Even with Clarke out of the picture, neither of the two other council members who are considered potential challengers indicated they intend to jump into the race.

Four years ago, the campaign for mayor was so vigorous that by April six major mayoral candidates were in the race and had amassed war chests totaling an estimated $1 million.

This time around, Barry has yet to attract a major opponent, he hasn't bothered to announce his candidacy and he has raised only about $150,000.

"The money is dribbling in and there's no one out there beating the bushes to raise it," said Max N. Berry, the mayor's reelection campaign chairman.

Two other potential challengers -- council members John A. Wilson (D-Ward 2) and Charlene Drew Jarvis (D-Ward 4) -- yesterday deferred their decisions on entering the mayoral race despite their earlier statements that it was the uncertainty of Clarke's intentions that was keeping them out.

"I don't think anyone of stature will challenge the mayor," said James Christian, chairman of the D.C. Democratic State Committee. "This mayor has a hell of an advantage. Several challengers don't think this is the time to challenge an eight-year incumbency."

"Everybody is basically sitting back and waiting for 1990," Christian added, on the theory that Barry might not run for a fourth term.

Wilson said he wouldn't rule out a run for mayor, although he earlier had said he probably would not run. Jarvis said she still has not decided whether she will challenge either Barry or Clarke, who intends to seek a second term as council chairman.

"A decision for Dave not to run is not the same as for me, because the person who sits in his seat is thought to be the natural inheritor [of the mayor's office]," Jarvis said. "I may just wait to decide."

"There needs to be a choice in the mayor's race," said Wilson. He said he does not have to make a final decision until next month. Earlier he had said that Clarke had blocked other candidates from entering the race, because supporters and contributors were waiting to see what he would do rather than being willing to pledge support to another candidate.

Clarke said yesterday that it is not too late for a major challenger to enter the race for mayor or council chairman.

"The mayor's race should not be foreclosed because of my decision to run for chair," Clarke said, adding that he believes Barry is vulnerable to a challenge.

Barry shrugged off Clarke's announcement as "expected" and contended that both Clarke and Wilson are "afraid" to enter the race.

"You don't need a poll to tell you that the citizens appreciate what I've done," Barry said.

Candidates filing under major party designations may begin collecting petition signatures May 9 and have until July 2 to file them with the D.C. Board of Elections and Ethics in order to appear in the Sept. 9 primary. A candidate running as an independent has until Aug. 27 to file to appear on the November general election ballot, according to D.C. Registrar of Voters Joe Baxter.

The announced candidates to date are former school board member Mattie Taylor, sex entrepreneur Dennis Sobin, health care consultant Brian Moore and accountant Calvin Gurley.

The mayor's lack of tough opposition also could have an indirect impact on some of the six city council campaigns other than the chairman's race. According to one theory, an easy race for Barry could free him to put his formidable machine behind his favored council candidates.

In Ward 6, for example, Theodis R. (Ted) Gay, former chairman of the D.C. Democratic State Committee, is considering a challenge to Democratic incumbent Nadine P. Winter but said the mayor's involvement could make a big difference there.

"My overriding major concern is the extent to which the mayor would work on behalf of the incumbent," Gay said recently, adding that he hopes Barry will stay neutral.

Clarke said he has not asked Barry for help in his campaign but that he would not refuse it, either. In 1982, Barry's campaign organization provided Clarke with some behind-the-scenes assistance in a tough three-way contest for council chairman.

"I have no arrangements with him," Clarke said.

In the meantime, Barry also is gearing up.

"The mayor's traditional corps of supporters is ready," said Christian. "I don't know if [Barry] has reduced it to writing, but I am fairly sure that all of the organization chieftains have been identified."

Barry, who is expected to formally declare his candidacy next month and name longtime political aide Anita Bonds as campaign manager, has formed a finance committee that recently opened a campaign office on Vermont Avenue NW.

The mayor last month included a a "special message" in a government mailing of application forms to city property owners for a homestead property tax exemption, urging them to take the tax break. The special message told residents of the administration's "improvements" in debt management, economic development, job programs, corrections and crime prevention.

In separate mass mailings, also paid for with city funds and targeted to specific neighborhoods, the mayor addressed more parochial concerns.

Under D.C. campaign law, certain types of promotional mass mailings by an incumbent elected official would be prohibited in the last three months of the campaign, according to Keith Vance, director of the D.C. Office of Campaign Finance. Annette Samuels, the mayor's press secretary, said Barry will refrain from issuing mass mailings at government expense during that 90-day period.

Barry's powers of incumbency and his perceived dominance ironically have made it a lot tougher for him to raise money this year. The mayor said earlier this year he would like to raise as much or more than the $1.3 million his campaign raised in 1982. But with no major challenger yet, the money has not been pouring in.

Fund-raising, Barry said after a news conference last week, "is harder because people say you don't have any major competition."

Last month, the mayor declared that he had banked more than $200,000 at a $1,000-a-plate 50th birthday breakfast March 6 and in the weeks following it. However, campaign chairman Berry said in an interview last week that the "$200,000 figure was overly optimistic."

"Any time you have a very exciting, close election . . . it's easier to raise money," Berry said. "A lot of people feel that if it's the opposite kind of race, why should we give money?"