CITY COUNCIL Chairman Sterling Tucker has been embarrassed, and rightly so, by the revelations of political favoritism and other abuses in the council's use of federal public-service job (CETA) funds. Under fire from the Labor Department and Sen. Patrick J. Leahy (D-Vt), Mr. Tucker this month scrambled for firmer ground by rushing some new CETA restrictions through the council Far from blunting the issue, his belated embrace of reforms has only underscored the previous abuse - including his own employment of a woman whose husband, a well-to-do dentist, is also treasurer of the Tucker mayoral campaign.

One might think that Mayor Washington, who has had problems with patronage himself from time to time, would just sit back and enjoy watching one of his principal rivals take the heat. Instead, incredible as it may seem, just three weeks before the District's primary the mayor has come galloping to Mr. Tucker's defense. First he joined the council chairman in asking Sen. Leahy to hold off any curbs on the local CETA program until the city had acted and Congress had produced a new national CETA bill. Then last week, the mayor approved a reply to the Labor Department that defended the council's performance in sweeping terms.

Two days later Mr. Washington did turn around and issue an executive order barring favoritism and political influence in CETA hiring, and adopting the salary ceilings and other rules that Sen. Leahy had initiated. By then, though, the mayor had given the issue away - and made his executive order look nearly as clumsy and face-saving as the council's response.

The mayor seems to have been tripped up by two things. One was his administration's habit of bristling defensively at any federal criticism of any city operation - regardless of how justified the challenge may have been or which local officials were at fault. Faced with the possibility of having to repay some hundreds of thousands of dollars in misspent CETA funds, the mayor reflexively circled the wagons around the City Council. Worse, he obviously failed to realize in time just how inappropriate and politically costly that reflex would be in this case. And so, unnecessarily, the mayor has managed to tar himself with Mr. Tucker's scandal, and in the process raise new questions about his own political acumen. CAPTION: Illustration, no caption, By Wright for [WORD ILLEGIBLE]