With filing petitions for this year's D.C. City Council races due tomorrow, political activists are choosing sides for what promises to be the hottest primary election this year -- the race to fill the Ward 7 seat now held by two-term Democrat Willie J. Hardy.

Candidates have been operating on the assumption that Hardy will not seek reelection. Hardy herself has been intentonally vague about her plans insisting only that "my mind is being made up for me" by constituents who have taken out petitions in her name.

Council seats in Wards 2, 4 and 8 are also up for grabs this year, as well as the at-large seats now held by Democrat John Ray and Republican Jerry Moore. But Hardy is the only council member who appears to be in serious political trouble and who would have to face well-known opponents -- a fact that observers say may be influencing her not to run.

At stake is the seat for most of far Northeast and Southeast Washington north of Anacostia. The ward contains the largest share of city public housing units and large numbers of low-income residents -- Hardy's power base. But it is also home to a rising number of black professionals, from whose ranks three other well-known candidates have come.

Johnny Barnes, a 32-year-old legislative aide to D.C. Del. Walter Fauntroy, has scheduled a press conference at the District Building this morning to present his completed filing petitions. Realtor H. R. Crawford, a former assistant secretary of the U.S. Housing and Urban Development Department already has filed his petitions.

Signatures also are being collected for school board employe Emily Washington, 36, who maintains that she has not yet decided whether to continue her campaign.

The candidates have said they will run for the seat regardless of whether Hardy decides to seek reelection because they feel she is vulnerable.

Hardy was the target of a brief, but well publicized, recall drive last year after she sponsored a pro-business bill to freeze worker's compensation benefits in the city. Organized labor and some Ward 7 residents were riled that the bill was, for all practical purposes, written by the Metropolitan Washington Board of Trade, and would have made deep cuts in workers' benefits.

It is unclear how much the worker's compensation bill may have hurt Hardy among her constituents, but her opponents, smelling blood, are saying she has lost touch with Ward 7 residents.

Ward 7 is two distinct subsections, divided roughly by Fort DuPont Park.

In the far northeastern and southeastern portion of the ward are families with income levels near or below the proverty line.

People on this side of the ward are concerned about the high cost of rental housing at a time when the council is debating at least three bills to replace the rent control law that expires in September.

"She [Hardy] has always had their grass-roots support," said Herb Barksdale, a Ward 7 community organizer for the Department of Human Services. "That is what always put her over. But I think she's lost that now. The people here don't see where the housing situation has improved any."

Among this segment, Crawford appears to have the greatest name recognition, an important asset, particularly in a city with a short history of electoral politics. Crawford is known in this area primarily as the manager of apartments for low and moderate-income residents.

Some of Crawford's business dealings have been controversial. The "Crawford Homes" project -- announced by then-mayor Walter Washington in March 1978 with much fanfare -- folded after 10 months, without providing any more housing for the poor and netting Crawford a $150,000 profit. Crawford has a reputation of beeing a strict landlord, enforcing thorough screening of new applicants.

The other section of the ward, south of the park in Southeast, is an enclave of new, black affluence. Homes on Westover Drive and Branch Avneue cost upwards of $100,000, and a new "Silver Coast" of black politicians, lawyers and businessmen in beginning to rival the uper 16th Street NW area as home for Washington's black elite.

Mayor Marion Barry recently moved to this part of the ward, and has been trying to establish a political base there. He ran third in Ward 7 behind Washington and Sterling Tucker in the 1978 mayor's race.

Barry is the political wild card in the upcoming race. He has been at odds with Hardy since she endorsed Tucker -- with harsh words for Barry -- in that often-bitter and highly personal mayoral contest. At one point during that divisive 1978 mayor's race, Hardy said of Barry: "As a flamboyant politician, Marion may be entertaining. But that won't cut it as mayor."

Del. Walter Fauntroy, Tucker, and Hardy have remained strong political allies since that hard-fought mayor's race, and the Ward 7 political observers say this year's council race will be a testing ground for Tucker, who may run for mayor again in 1982.

Attention quickly focuses on Barnes, Fauntroy's legislative aide. Barnes said he is aware of the charges that he is Fauntroy's handpicked candidate and a stalking horse for Tucker. He replies only that "I'm going to have enough trouble getting Johnny Barnes elected without having to worry about Sterling Tucker."

Barnes is one of the "new breed" of Washington politician, a recent transplant bringing a lawyer's training to local problem-solving. Barnes said he sees the need to bring "creative ideas" to the council, and cites his contribution to the fight for full voting rights for District residents as a prime example.

Barnes wrote the voting rights amendment that was introduced by Fauntroy and passed by Congress. It is now stalled in the ratification process in statehouses around the nation.

His strength as a vote-getter is relatively untested. His only brush with elective politics came when the D.C. Democratic State Committee chose John Ray over him to fill the City Council seat vacated by Barry's election as mayor.

Washington, by contrast, gave an impressive showing in an unsuccessful school board race last year. A relatively unknown teacher from Ballou High School, Washington piled up 1,804 votes -- 35 percent of the total -- against Nathaniel Bush, who won with 2,180 votes.She is now viewed by many as one of the District's up-and-coming young politicians.

Crawford also was skipped over by the Democratic party when it was filling Barry's council seat. Crawford also entered the fray in 1978, losing a close, and often acrimonious, at-large council primary to Democrat Betty Ann Kane. The vote that year split largely along racial lines, and in the predominantly black Ward 7, Crawford beat Kane with 4,903 votes -- 757 more votes than Hardy got when she won reelection in the ward two years earlier.

Crawford expects to spend about $30,000 in his campaign, and already has raised about $7,000, according to his treasurer, Monteria Ivey Sr. Ivey was director of the city's public housing program under Walter Washington, but was fired by Barry.

Barnes expects to spend $35,750 to win the seat. He has raised between $10,000 and $12,000, from a fundraiser at the Northwest Gardens apartment and an auction, and from a $3,500 direct mail effort, according to treasurer David Wilmot, an attorney and former law partner of Barnes.

There are 29,655 registered voters in Ward 7, almost all of them Democrats. Ward 7 Republicans, it is said, could hold their meetings in a telephone booth.

In the other wards, John Wilson (D-Ward 2): Wilhelmina Rolark (D-Ward 8): and Charlene Drew Jarvis (D-Ward 4) all are facing only minor opposition. Democrat Ray is considered a shoo-in for his at-large seat, and Moore, the council's only Republican as well as its only clergyman, has been endorsed for reelection to his at-large seat by five of his Democratic colleagues.