Its final week has brought the New York primary campaign to its climactic pitch as hysteria rampant upon a field of apathy. Morning came to a city hall bereft of two of its three most conspicious ornaments:

George Washington's desk was still in place, but the mayor and the president of the city council had left for the Astoria Studios to quarrel at the invitation of the Daily News.

A visitor girded on his headsets to absorb proceedings in which the closest approach to interludes of triumph belonged, of course, to Herman D. Farrell, since it is a general rule for such terminal feasts of reason and flows of the soul that their debates are won by the party with the smallest chance to win anything else.

Still, the occasion was more striking for its sidelights than for any high ones. It could be noticed that each mayoral joke evoked laughter from the audience distinctly outsized for its deservings. There is no denying that the mayor can be an amusing fellow, but no one is that unvaryingly boffo.

If Louis XIV had thought to lighten his levees with a jape or so, we may suppose that the response would have had rather the same dutifully unbuttoned hilarity.

It could be noticed too on a prowl about city hall that, except for the mayor's own pressroom, which has to stay alert for emergency demands for damage control, not a radio had been turned on and tuned in except the visitor's. Here at the campaign's very pulse, nobody was listening.

Then the mayor came back to be not just highly visible but inescapable. A press conference had been gathered by Women for Bellamy and featured Bella Abzug, a personality some think more kinetic than her candidate. When the president of the city council came to greet her partisans, there was the mayor not 10 feet from her on the city hall steps. The poor sister cannot mount the most modest parade without the mayor plunging in to upstage it.

He cannot, to be sure, be blamed for this unappetizing posture; he is in the throes of the fit that overcomes the candidate who, assured of the majority, lusts after the unanimous.

He had brought off this distractive maneuver by talking about AIDS, a subject about which he, like most of our public personages, appears disciplinedly to have missed the point.

When we speak of those suffering from AIDS, we talk about young men probably doomed and, if not, by all known evidence so vulnerable as to be far more menaced than menacing.

So far as the doctors know, an AIDS patient can cough in my face and I risk a slight cold, but if I cough in his, he can get pneumonia. And yet we have become so obsessed with their fancied danger to us that no politician dares to talk about the special horror of treating victims as pariahs.

Last Wednesday, David Rothenberg gathered members of the Coalition for Gay Rights to protest the mayor's shuffling off of the city's responsibility to establish an AIDS hospice to the Archdiocese of New York. Their complaint was sound; AIDS challenges not just one church but all the rest of us.

What was curious and even sadder was the chill with which the Gay Coalition greeted Cardinal John O'Connor's initiative.

"If the archdiocese wants to run and fund its own AIDS center," said Andy Humm, "that is their privilege." The cardinal is indeed not surprisingly stiff- necked on the subject of continence and the Gay Coalition has been understandably wounded by his prior comments and present policies. But he is not availing himself of a dubious "privilege"; he is acting upon a concept of charity lamentably absent everywhere else. Of course it is sinful to lay what is our duty all on his shoulders, but we ought not to blame him for trying to do the good deed that every other visible institution seems to abjure.

The mayor was in happier form at the ceremonies of tribute to Cab Calloway. Calloway led all present in the "Hi Dee Ho's" of the tale of "Minnie the Moocher" and her beloved Cokey Joe, and the mayor chanted louder than the rest, all unconscious that he was hymning the weed, the gage, the Good Brother, and the Mary Jane.

He and Cab Calloway had brought the reefer to City Hall Park, which, judging from the fumes that cloud it in the spring noons, amounted to carrying coals to Newcastle.

A group of Brooklyn residents assembled to object to a proposed incinerator stood on the other side of the police barriers, their outcries drowned in these hosannas to pot.

The mayor has reached the summit where candidates are immune to damage; on a day when he may have lost some of the Hasidim, he had recouped with the drug culture.