In the race for an open citywide seat on the D.C. Council, one tactic has become part of each Democratic candidate's campaign: To rebuke, or at least publicly avoid, the city's political establishment.

Linda Cropp, widely regarded as the front-runner in the Sept. 11 Democratic primary for the at-large seat being vacated by Democrat Betty Ann Kane, speaks of her experience as a Ward 4 school board member, but promises to be "fresh blood" in city politics. She rarely notes that her husband, Dwight Cropp, for years was a top assistant to Mayor Marion Barry, or that she ran with Barry's tacit support for the council in 1988.

The two other Democrats in the race, lawyer Johnny Barnes and tenant activist Terry Lynch, make similar pitches. Barnes, who for years was chief of staff to D.C. Del. Walter E. Fauntroy, doesn't cite Fauntroy in any of his campaign materials. Lynch, meanwhile, bills himself as "the Washington Board of Trade's worst enemy."

With six weeks of campaigning left, the race for the at-large seat, left open when Kane opted to run for D.C. delegate, is emerging as one of the most aggressive, and caustic, political fights in the city.

The candidates are all reciting familiar populist themes: opposition to a tax increase, promises of improved schools and housing, and pledges to help economically depressed areas. So the primary may hinge on who shows the most energy and imagination.

Another at-large council seat, held by veteran Statehood Party member Hilda H.M. Mason, is up for election this year. Mason is running unopposed for the Statehood Party nomination in the primary, while W. Cardell Shelton, a contractor, is running unopposed in the Republican primary for an at-large seat.

Mason, Shelton and the winner of the Democratic primary will appear on the November general election ballot, along with several independent candidates who are bypassing the primary. The top two vote-getters in the general election will fill the two at-large seats.

Some political observers say that Mason, 75, may be vulnerable to the hard-charging independents who say it's time for her to retire.

The independents in the race include Ray Browne, a Georgetown community activist; Jim Harvey, former administrator of the Whitman-Walker clinic; and Clarene Martin, a labor lawyer and community activist.

For now, the key battle is among Democrats Barnes, Cropp and Lynch. They are fielding formidable organizations, and are hammering at one another's records.

Cropp, a school board member since 1980, is running with the support of the Washington Teachers Union, the D.C. Firefighters Association, the D.C. Realtors Association and the Gertrude Stein Democratic Club, a leading gay political organization in the city. She also has established close ties to D.C. Council member John Ray's mayoral campaign.

"I will be fresh leadership on the council," Cropp said. "But I will bring years of experience from the school board."

That experience is criticized by Barnes and Lynch, who say that she is a reticent board member who has not fixed many school system problems. "Can anyone say with a straight face that schools are much better now than they were 10 years ago?" Lynch said. "I don't think so."

Barnes said: "She has been on the board for a decade, but schools are still in crisis."

Cropp counters by saying that the city needs a council member who recognizes the value of education. Her chief campaign pledge, though, is to attack waste and inefficiency in government. She advocates cuts in the D.C. work force: "We need a government with less managers and more management."

Barnes agrees, saying he would start "at the top levels of government." Yet neither Barnes nor Cropp has said how many jobs they want to eliminate if elected.

In his campaign, Barnes is stressing his city roots and his concern about environmental issues. "I've lived in every ward," he said. "I know people's needs." He also highlights his career on Capitol Hill, where he has been senior counsel for the House's District of Columbia Committee. But he does not mention that he also was Fauntroy's administrative aide.

Why not? "I don't want to inject myself into the mayor's race," Barnes said. But Cropp and Lynch suggest that Barnes is avoiding any link with Fauntroy for fear it will cost him votes.

A few weeks ago, Barnes challenged Cropp and Lynch to take a drug test. "I think it's a very positive step for an official to say, 'I'm drug free,' " Barnes said. But his action was denounced. "It was a self-serving publicity stunt," said Cropp, who still took a drug test.

"His campaign is going nowhere, so he's latching onto a hysterical tactic," Lynch said.

Barnes and Cropp have run for the D.C. Council before and lost. This is Lynch's first bid for elective office. Since 1985, he has been executive director of the Downtown Cluster of Congregations, a coalition of 27 churches organized to protect housing and small businesses in downtown Washington.

Lynch, 31, is the youngest candidate in the race. He has enlisted one of the city's most prominent civic activists to manage his campaign, Lawrence Guyot. Guyot has long been one of Barry's key community organizers.

Nevertheless, Lynch boasts of not being tied to "any machine or special interest," and has pledged to provide more affordable housing and to protect tenants' rights. He also has harsh words for current D.C. Council members, saying they are "controlled by campaign dollars from the Board of Trade."

But Lynch, a Mount Pleasant resident, is facing questions about his lack of experience in city politics. "We need someone on the council who won't need on-the-job training," Barnes said.

Lynch also trails in raising funds. As of last month, according to figures reported to the D.C. Office of Campaign Finance, Lynch had collected about $8,100. Barnes and Cropp each have raised about $27,700.