Leading District of Columbia Democrats, in an attempt to head off the kind of election-year party divisiveness that took place in the presidential primary in 1976, are carrying on intense behind-the-scene negotiations to pick a unified slate of candidates for seats on the D.C. Democratic State Committee.

According to sources, the talks involving political rivals were initiated in an attempt to remove Carter vs. Kennedy presidential politics from the election of committee members, which will take place in the May 6 District Democratic primary.

The committee directs policy for the local Democratic organization, in some cases chooses interim members of the City Council, and is sometimes consulted by the White House regarding federal appointments that affect the District of Columbia. Forty-four seats on the committee will be filled in the primary, along with the posts of Democratic national committeeman and committeewoman and alternates for those two slots.

A similar attempt to hammer out a unified slate failed in 1976. As a result, there was a bitter clash between the "Open Party" slate, headed by Mayor Walter E. Washington, and the "Unity '76 Coalition," led by Del. Walter E. Fauntroy, City Council Chairman Sterling Tucker and Marion Barry, then a member of the Council.

Sources said a major hurdle in this year's unity effort was cleared at a meeting of leading Democrats last Saturday, when it was agreed that each citywide official would be allowed to place on the slate a number of candidates for the 12 at-large committee seats.

Mayor Marion Barry was allowed to pick four candidates, the sources said, while Fauntroy, City Council Chairman Arrington Dixon, and at-large council members John Ray and Betty Ann Kane were permitted to pick two candidates each.

Each ward council member was allowed to pick three out of four ward candidates, according to the sources. The fourth candidate from each ward was selected through negotiations between the ward council members and the citywide officials.

The negotiations have broken down, however, over the selection of candidates for committeeman, committeewoman and alternates.

The major issue, according to sources close to the talks, is whether Sharon Pratt Dixon, a Pepco lawyer who is wife of the council chairman, will be named to retain her post as committeewoman. Barry has attempted to keep her off the slate but Dixon said she will run no matter what.

The attempt to forge the single slate began more than a month ago as officials and party leaders began announcing their choices in the presidential contest.

Barry and Dixon support President Carter, while Fauntroy, Ray and Kane all support Sen. Edward M. Kennedy (D-Mass.).

"There had been a lot of discussion for a long time about having so-called 'Harmony' slate," Ray said. He said the idea was that a single slate would not "allow us to be ripped apart" by presidential politics.

Last week, Barry authored a full slate of his own, sources said. A Barry supporter said the list was "for discussion purposes only." It was soundly rejected by the other officials at a meeting last Thursday in Council Chairman Dixon's office.

At a subsequent meeting on Saturday, Barry, Dixon, Kane, Ray and Fauntroy followed the allotment procedure strictly, sources said.