THEY cleared the basketball players out of the old Cambridge armory (now an M.I.T. gymnasium) last Sunday night to make way for several hundred small round tables, each with a white and a red carnation in the center and neat white programs with the cartooned image of Cambridge Mayor Walter J. Sullivan on the seats. It was a "do" (testimonial dinner) for Sullivan, perenially the top vote-getter in City Council elections.

Dinner--"to be served at 6:30 p.m. sharp" as the invitation said--didn't begin until after seven, but the sodality ladies, school teachers, and even the Somerville policemen religiously refrained from dipping into their fruit cups until after the Bishop of Boston delivered the invocation. Meanwhile, Ruby Newman's Orchestra, attuned to the niceties of the affair, balanced "When Irish Eyes are Smiling" with "Arrivederci Roma" as they played from the balcony.

Walter's older brother Edward (a former Cambridge mayor) was the toastmaster. The "galaxy of stars at the head table" (and lesser lights in the audience), whom he introduced bore the family names that count in Cambridge politics--O'Neill, Crane, Danehy, Lynch, and Good, to name a few. Some had gone to St. Paul's School with Walter; others were his near or distant relatives; all were his political allies, at least for the moment.

They rose, thanked the "reverend clergy, distinguished guests at the high table, ladies and gentlemen," and praised "Walter's lovely wife Marion and his five wonderful children." A few evoked memories of Sullivan's late father, Michael A. "Mickey the Dude" Sullivan, who founded the Sullivan political dynasty. "He must be looking down from heaven, happy that there's not a warmer person in public or private life than Walter," was how one speaker put it.

During one particularly effusive tribute a voice--perhaps over-enthusiastic, perhaps cynical, but undoubtedly loud--shouted "Shoot (push) him for governor" from the back of the room.

The Honorable Howard W. Fitzpatrick, High Sheriff of Middlesex County, was there. Some said the dinner had originally been planned as a kick-off for Sullivan's campaign to succeed the supposedly retiring Fitzpatrick as Sheriff, but when "Howie" decided to run again, the "do" became just a "tribute to a good man." Fitzpatrick wished Sullivan "God's choicest blessings." In return, Walter reminded the crowd that "I'm one of Howie's campaign managers. He's running for re-election--don't forget that."

IT WAS, to be sure, a bit exhausting. Clouds of smoke and a few glazed stares from the 2500 guests greeted the main speaker, Superior Court Judge Francis J. Good, as he praised "one who rose from the ranks of the people--a friend of the man in the streets, member of a family famed for its industry, its sincerity, and its integrity." Good, like Sullivan, went to St. Paul's School and he noted with pleasure that "St. Paul's is still Walter's home base."

Sullivan himself looked even nattier than he does each Sunday when, as St. Paul's head usher, he greets parishoners at the door. Silvery hair and glasses gleaming, he bounced from table to table greeting friends and allies. With a broad smile, he accepted flowers from a Democratic committee-woman, a scroll from the Michael A. Sullivan Memorial Associates (a continuing Sullivan campaign organization), a chair from the committee of friends giving the dinner, and a fire-helmet from the Cambridge Fire Department. "It's his smile; he'd win it on his smile alone," one woman said as he beamed at the audience.

Rising for a few additional remarks. Sullivan noted that his physical fitness director at the "Y" was waiting outside to run off the dinner. And then he quoted Adlai Stevenson: "'The best of one's life is one's friends'--tonight has proven the truth of that remark."

As for the food--well, it was no better than it should be.