BY ANYONES ACCOUNT, Gladys Noon Spellman entered the race for reelection to a fourth term in Congress as the most popular politician in Prince George's County. Today, that reputation has not changed a bit -- but, as Mrs. Spellman's millions of admirers in the county, in Congress and throughout the Washington region have had to accept -- her own circumstances have. her remarkable 19-year political career has been halted, though it remains a classic for all who would seek public office and serve successfully.

To have watched Mrs. Spellman on the campaign trail, on the phones, in the schools or up and down the aisles and office hallways of Congress was to see a woman obviously reveling in her work and loving her constituents. You could watch with amusement, too, as Mrs. Spellman would bat those big dark eyes, smile, gosh-golly it a few times -- and then systematically trip the socks off of unsuspecting colleagues in the House to make another point or two on behalf of her constituents.

There has always been more to it than charm and cunning, through; mrs. Spellman has been a political pro in every way, with an uncanny sense of her constituency's interests -- most notably those of federal employees, from elevator operator to secretary, clerk and middle-level professional. To this group that always suffers as the they target of the "anti-Washington" candidates, what better music than Mrs. Spellman's "Beautiful Bureaucrat" column in her newsletter, commending "wonderfully responsive" government workers and championing those who, "far from slowing down the wheels of government, are really the people who keep them churning"?

This keen appreciation of her constituents and of government at its best has been instrumental in promoting the best of Prince George's County -- where Mrs. Spellman first came into the public eye as a crusading PTA activist, elected as a Democratic reformer to the old County Board of Commissioners in 1962. Four years later, she became board chairman, the first woman to head Maryland's largest county. Mrs. Spellman remained in the political thick of things when the county changed to a charter form of government, winning election to the new county council and, in 1974, to the U.S. House.

The bubbling omnipresence of Gladys Spellman -- in meetings large and small, at those open-door complaint sessions for constitutents, at the nightly sessions throughout her district, at the PTAs, at the clubs or in the family rooms around the neighborhoods -- is no more. And yesterday's declaraion of a vacancy of this seat was only right, for representation of this district must continue.

Still, we can know what Mrs. Spellman's daughter means when she says, "I'm waiting for her to look up and tell me to cut my hair, or to tell the boys to trim their beards." After all, everybody knows by now that Gladys Spellman has never been one to be underestimated.