No sooner had U.S. Supreme Court Justice Potter Stewart announced that he will retire next month than Sen. Dennis DeConcini was campaigning for Sandra O'Connor of the Arizona Court of Appeals as a worthy replacement.

DeConcini's quick move made sense. For President Reagan has said he will move quickly to fill the vacancy, hoping the Senate can confirm his appointment before the high court reconvenes in October. The promotion of a qualified woman jurist also made sense, because Reagan has indicated the Supreme Court will seat its first female member during his administration. Actually, Democrat DeConcini, who seldom misses a political trick, stole the march on Sen. Barry Goldwater. It would seem that Republican Goldwater should have seized the opportunity to drop the name of Mrs. O'Connor, a conservative Republican and a near-neighbor from Paradise Valley. In any event, Tucsonian DeConcini, facing a statewide re-election race in 1982, no doubt endeared himself to many people in Maricopa County through his alertness. Mrs. O'Connor, 51, an appellate court judge since 1979, is highly regarded. We trust Reagan will give Mrs. O'Connor careful consideration. We were impressed by her five-year performance as a state senator (1969- 74), especially her final two years as a bright and effective Senate pres ident, and we have heard good reports of her even-handedness as a judge, beginning with her Maricopa County Superior Court stint (1974-79). As a clear sign of her popularity, Mrs. O'Connor