By air, by land, and by mail, the three Democrats vying for a citywide seat on the D.C. Council will make a last-ditch attempt to lure voters over the next few days in what many say has become a tight race.

Johnny Barnes, a lawyer and former congressional aide, will take his campaign to the skies Sunday by having a plane swirl over Robert F. Kennedy Stadium during the Washington Redskins' season opener and tow a banner displaying his name.

Linda Cropp, a school board member with close ties to mayoral candidate John Ray's campaign, is distributing brochures Saturday and Monday to voters on every block.

Meanwhile, Terry Lynch, a housing activist, has begun a series of radio ads and on Saturday will conduct what he calls a "Tour of Shame" through D.C. neighborhoods that either feel threatened by commercial development or suffer from neglect.

Six council seats are up for election, and in most the incumbents seem assured of victory in Tuesday's Democratic primary. But the at-large race between Barnes, Cropp and Lynch -- all eager to fill the influential post that Betty Ann Kane has vacated -- remains combative, heading into the final stretch.

Cropp, making her second bid for a council seat, is regarded by many political observers as the front-runner, but still vulnerable to the hard-charging Barnes and Lynch.

The Democratic winner then must face a host of independents, including Mayor Marion Barry and incumbent Hilda H.M. Mason (D-Statehood) in the Nov. 6 general election. The top two vote-getters will win council seats. Mason is already gearing up for the fight with Barry; she has a $72,000 war chest -- $60,000 of which she has lent to the campaign.

Cropp, 42, has moved closer to Ray's mayoral campaign (at times they share campaign vans) while assuring voters that she will be an independent voice. She emphasizes the same themes as her competitors -- efficient city services, less government fat -- but claims she has more experience.

Cropp, whose husband, Dwight, was a top aide to Barry, also is attempting to assure voters she has no ties to his political machine.

At a forum in the key Shepherd Park precinct of Northwest, Cropp said that as a school board member she "sued the mayor of this city three times successfully."

"Our momentum seems to be just right," Cropp said this week. "We've got a broad base of support."

Barnes, 43, a longtime aide to Del. Walter E. Fauntroy and counsel to the House District of Columbia Committee, is also running hard. He has spent about $70,000 on the campaign ($23,000 of it was his own money), and earned the endorsements of several tenant-rights leaders and the Rev. Willie F. Wilson, the pastor of Union Temple Baptist Church in Anacostia.

As the campaign closes, he is insisting that Cropp is not the front-runner. "She has rested on her laurels," Barnes said. "Terry Lynch and I have been more places and touched more voters."

Lynch, 31, an activist for housing and the homeless, has raised about $30,000, has endorsements from the Sierra Club and tenant leaders, and is telling voters that he is an enemy of developers and the Greater Washington Board of Trade, which he accuses of neglecting the poor.

"Voters are sick and tired of what's going on in D.C., and the only way to clean house is to vote for me," Lynch said.

In the other council races, incumbents are running with much more money and endorsements than any of their challengers. One close race may be in Ward 6, where incumbent Nadine P. Winter is fighting off aggressive challenges from several candidates, especially Harold Brazil and Bernard Gray.

Brazil, a former lobbyist with the Potomac Electric Power Co., has raised about $35,000. Winter has raised $52,000.

In the race for council chairman, a job that mayoral candidate David A. Clarke is leaving, Ward 2 council member John A. Wilson has collected about a half-million dollars. Political newcomer Vincent Orange has run a spirited campaign, but has raised less than $25,000.

In Ward 1, two-term council member Frank Smith Jr. appears headed to victory over local lawyer Richard Landis, whom he easily defeated in 1986. Although there is discontent about Smith's council performance in many parts of the ward, Landis's campaign lacks fervor. He has raised about $10,000.

In Ward 3, incumbent Democrat Jim Nathanson is running without opposition in Tuesday's primary. And in Ward 5, incumbent Harry Thomas Sr. is facing challenges from three opponents, but Democratic leaders expect him to win.