Mayor Marion Barry remains significantly ahead of his chief challenger for the Democratic mayoral nomination in the Sept. 14 primary, Patricia Roberts Harris, while the three Democratic candidates for the City Council chairmanship are nearly even, according to a new poll released yesterday.

The poll, conducted last Wednesday and Thursday by WRC-TV and the Associated Press, was based on interviews of 407 Democrats who have regularly voted in the city in the past and said they plan to vote in the upcoming primary.

In the mayor's race, the poll showed Barry with 50 percent support and Harris with 34 percent. Council member Charlene Drew Jarvis (D-Ward 4) had 3 percent and council member John Ray (D-At large) had 2 percent. Ten percent were undecided.

The poll showed council member David Clarke (D-Ward 1) as having gained support in recent weeks to draw into a close, three-way contest for council chairman with incumbent Arrington Dixon and former chairman Sterling Tucker.

Clarke now has 26 percent support while Dixon has 30 percent and Tucker 27 percent, according to the poll. All three candidates fall within the 6 percent margin of error for the poll, putting them in a virtual deadlock. An earlier poll had shown Clarke trailing significantly.

"I'm going up and they Dixon and Tucker are going down, and I think that will continue," Clarke said of the poll's findings.

Dixon contended, however, that Clarke's rising support is of no consequence. "We're ahead and I'm never concerned about being ahead," he said, adding that he believes Tucker's support is "depleting and fading out as they did in his earlier efforts to run for mayor." Tucker could not be reached for comment.

The WRC/Associated Press polling group conducted two earlier polls of the mayor's race but used different methodology, which means that those results are not strictly comparable to the results of the current poll. The group's first poll in April showed Harris leading Barry by 11 percentage points, and the second, released in July, showed Barry with a slim lead of four points.

The latest poll's findings in the mayor's race are nearly identical to those of a late-June poll of registered Democrats by The Washington Post, which showed Barry with a 13-point lead over Harris, and Jarvis and Ray with little support.

Regarding the City Council chairman's race, however, the new WRC/Associated Press poll differs widely from the Post poll. In The Post's poll, Clarke registered only 16 percent support, while Tucker had 31 percent and Dixon 28 percent.

The latest poll echoed the earlier findings of The Post's poll that Barry holds a lead among black voters while Harris leads among whites.

When the WRC/Associated Press pollsters asked respondents who they believed would win the mayoral nomination regardless of how they themselves planned to vote, 79 percent said Barry, 12 percent said they were not sure and only 7 percent said Harris. Jarvis and Ray were believed likely winners by only 1 percent each.

The poll also asked respondents to evaluate Barry's performance in office and included responses from all 973 voters reached, not just the 407 whose responses were counted in measuring support for the various candidates. Only 9 percent said Barry has done an excellent job but 34 percent rated his performance as good, with a plurality of 37 percent saying the mayor's performance had been "only fair." Fourteen percent said he had done poorly and 6 percent said they were not sure.

Barry's campaign press aide, Lea Adams, said Barry would have no comment on the poll.

Harris released a statement saying: "We said all along we were the underdogs and we will fight for every vote until election day. Polls don't decide elections, people do."

Jarvis said she still does not think Barry will win the race. "What you are seeing is a tribute to an incumbent who people are afraid of, who has raised a million dollars and who has used the city treasury as his private kitty," she said. "I don't think he will win."

Ray, who was campaigning yesterday on Good Hope Road, said he believes he will win the race by getting 33,000 votes. "The poll would have us believe that if 100,000 people vote in the Democratic primary I would get only 2,000 votes," Ray said. "That is absurd on its face. Approximately 106,000 people voted for me in my 1980 general election council race."

In another campaign development, Harris continued to attack Barry's economic development record yesterday, claiming that the mayor has not done enough to attract new businesses and jobs to neighborhoods surrounding the downtown area.

She said one of her top priorities would be to oversee development of light industry, grocery stores and shopping centers along New York Avenue, a depressed corridor of Northeast Washington that has about 240 acres of empty or unproductive land.

"For 10 years we've been talking about what we could do with it," Harris told reporters at a vacant lot near New York Avenue and First Street NE. "Now it's time to stop talking and to act."

Noting a sharp decline in the number of supermarkets and grocery stores in Washington, Harris said: "The only response of the Barry administration has been to bus our elderly residents to Maryland" to shop.

Harris stepped up her criticism of Barry for refusing to take part in a prime-time televised debate the week before the primary election.

"We now have a situation where our mayor only wants to discuss serious problems in an 'informal chat,'" she said. "With this attitude, it is obvious that the critical issues facing the District will not be addressed. The mayor wants a sideshow, but the voters have a right to know what the candidates plan for the next four years."