AN IMPORTANT CITY COUNCIL election comes up on July 19. Under the city charter, a special election is required to fill the at-large vacancy created by the death of Julius Hobson Sr. in March. Hilda Mason, a diligent, thoughtful and knowledgeable public servant has held the seat temporarily by appointment. We think she ought to have the job on a more permanent basis - by election.

While Mrs. Mason is her own best argument for election, the possibility of a victory by any of her opponents strengthens her case. Of these, the two most prominent contenders are Susan Truitt and Barbara Sizemore, and neither comes close to matching Mrs. Mason's record of community service.

Mrs. Truitt is a former loyal spokesperson and apologist for the monumentally inept human-resources administration of Joseph P. Yeldell. Mrs. Sizemore was the embattled school superintendent whose pre-occupation with racial innuendo and confrontation overshadowed an abominable administrative record. Mrs. Mason, as a member of the school board, joined the majority in firing Mrs. Sizemore and selecting Vincent E. Reed to restore order and to clean up the bureaucratic rubble she had left.

In her brief span on the city council Mrs. Mason has demonstrated an impressive grasp of local issues. At least five members of the council are actively supporting her candidacy now: Chairman Sterling Tucker, Marion Barry, David A. Clarke, Polly Shackleton and John A. Wilson.

The election is two weeks away. We bring it up now to alert you to the event and to the importance of the choice to be made. It is not too early for interested citizens to lend a hand in this campaign - or to apply to the board of elections for an absentee ballot (you may also vote in advance in person at the board office) if you plan to be out of town on election day.