Supporters of D.C. City Council member Hilda Mason asked the D.C. Board of Elections and Ethics yesterday to remove from the July 19 special election ballot the names of lthree other candidates, including independent Susan Truitt.

The Mason supporters contended that the nomination petitions of Truitt and two persons running as Statehood Part candidates - Frank E. Sewell Jr. and Naomi VanderJagt -do not contain enough valid signatures to meet the minimum number required by city election law.

On its surface, the challenge to Truitt appeared to be a serious one. It asserted that at least 1,076 of the 3.621 signatures she submitted came from persons who were either not listed on the city's current voter rolls, or who provided inaccurate or inconsistent information in signing petitions.

In addition, the challenge asserted that three of the persons who circulated petitions for Truitt were not registered D.C. voters, as Mason supporters believe is required by law, and that the names of nine others who gathered signatures are not on the D.C. voter rolls.

Truitt, who needs 3,000 valid signatures to remain on the ballot, said yesterday that she believes she has enough valid signatures to avoid disqualification. "If that's what we're playing," she said, "I'm sure we can beat it back."

Truitt acknowledged that three persons cited by challenger Gwendoline Graham Reiss, a Republican working as a Mason Volunteer, probably are Maryland residents, as Reiss claimed. The city's election regulations say that any person circulation petitions must be "a duly registered voter" but the place of that registration is not specified in the regulation.

Sources familiar with the city's election records also say that some of the city's voting records may be in such hopeless disarray tha exact registration would be impossible to check.

Yesterday's challenges were the only three made during the 10-day period (ending yesterday) that city election laws allow to contest the validity of petitions. Mason was appointed to her seat, pending the special election, following the death March 23 of Julius Hobson Sr.

For thepast several days, Mason supporters have been combing through the petitions. At one point, according to a Mason supporter, consideration was made of challenging the candidacy of former school superintendent Barbara Sizemore, whom some consider one of Mason's stronger opponents.

Size more, however, had more than 5,000 signatures - she needs only 3,000 valid ones - and a challenge to her seemedfutile, the Mason supporter said.

All four of the independents besides Sizemore turned in about the same number of signatures. But Mason supporters chose to challenge Truitt becasue some believe the former television reporterruitt because some believe the former television reporterndents - Richards Clark, Wade Jefferson and James Clark.

The candidancy of Sewell, a former Democrat, was challenged by the D.C. Statehood Party, which has endorsed Mason.It contends that at least two of the 20 signatures submitted by Sewell are invalid. Sewell needs 18 valid signatures to remain onthe ballot.

The Statehoold Party also challenged thepetitions submitted by VanderJagt, contending that not one of the 32 signatures she turned in to run as a Statehoold Party candidate came from persons who are registered as Statehoold Party voters.