Democrat Ruth Dixon, a newsletter editor and publisher, officially announced her candidacy yesterday for the D.C. City Council seat being vacated by council member Polly Shackleton (D-Ward 3).

Dixon predicted schools, housing and development will be the main issues in the Ward 3 campaign.

At an announcement party attended by several hundred supporters, she said she would like to see more incentives to build rental housing in the ward, declaring: "We haven't had any building of rental housing in 10 or 12 years."

Dixon said her support of legislation passed by the council last year to ease rent controls, and her opposition to a referendum restoring the stricter controls, meant that "I was ahead of my opponents" on the issue. While the referendum narrowly passed in November, Dixon noted that 63 percent of Ward 3 voters opposed it.

Dixon, 64, ran for the Ward 3 council seat in the 1982 Democratic primary, coming in second with 35 percent of the vote to Shackleton's 47 percent. A third candidate that year, Mark Plotkin, got 18 percent of the vote in the primary and last week announced his candidacy for the seat again this year.

Shackleton has endorsed a third Democratic candidate, Jim Nathanson, a teacher at the Duke Ellington School of the Arts who has been chairman of the Ward 3 Democrats.

On that endorsement, Dixon said yesterday, "I just hope she is as successful now as she has been in the past," referring to endorsements Shackleton has made of several losing candidates.

Mary Draper Janney, a former leader of Wider Opportunities for Women and Planned Parenthood of Metropolitan Washington, also has entered the field of Democratic candidates.

On the Republican side, only Gloria R. Corn, an advisory neighborhood commissioner and Forest Hills resident, has said she plans to run.

Dixon is a former president of the D.C. League of Women Voters and formerly chaired Advisory Neighborhood Commission 3F, in Ward 3's North Cleveland Park/Forest Hills area. She started publishing the District Council Journal in 1983, reporting and writing the newsletter. She has a master's degree in political science from George Washington University.

Dixon, noting that Ward 3 has the highest concentration of elderly in the District, said that the city should provide senior day care centers to provide respite for adults trying to care for elderly parents.

The Democratic primary is Sept. 9.