A city-paid public relations consultant has enlisted the widow of Martin Luther King Jr. and several sports figures to help turn out the largest possible vote in the District of Columbia's Sept. 12 primary election.

Ofield Dukes, the consultant, told a meeting of Washington broadcasters yesterday that Coretta King has tape-recorded a message for radio and television. Others joining the campaign will include golfer Lee Elder and former football players Roy Jefferson and Larry Brown.

The D.C. League of Women Voters has produced more than a dozen television spots, including some addressed to the deaf in sign language.

Dukes said this year's primary and general elections in Washington will be especially critical because of the pending ratification of the constitutional amendment to grant D.C. voting representation in Congress.

"Those 38 states that must ratify will be watching and checking on the number of people who will be going to the polls," Dukes said. If the turnout is low, he said, "some are likely to use it as an excuse against ratification."

Dukes will be paid about $13,000 by the D.C. Board of Elections and Ethics for a voter education program for both elections.

There were those other election developments.

The Board of Elections announced that there are [WORD ILLEGIBLE] registered voters in the city, with this party breakdown: Democratic, [WORD ILLEGIBLE] republican, [WORD ILLEGIBLE] Statehood, [WORD ILLEGIBLE] U.S. Labor, 53; Socialist Workers, 79; other parties not holding primaries, 1,357, and independents, 27,463. The total is down from the 1974 mayoral primary election, when there were [WORD ILLEGIBLE] registered voters.

The Board of Elections announced deadlines for voting by absentee ballot in the primary election. Those who want to ask for a ballot by mail must send a request to the board by Tuesday, and send the ballot back to the board by next Friday. Others may vote in person at the board's office Room 7 of the District Building, 14th and E streets NW, until 5 p.m. next, Friday. For information, telephone 347-9725.

The board also said seven candidate have filed petitions seeking to be placed on the Nov. 7 general election ballot as independents.

The seven persons are: Charlotte J. Reavis, for delegate in Congress; Glova E. Scott, for mayor; the Rev. Warren A. Hemphill Sr. and Raymond W. Powell, for City Council at-large; Jonathan M. Owens, for City Council ward 5, and Charlotte R. White Holmes and Sonny Better, for City Council Ward 6.*