The huge, gray City Hall on La Salle Street was like a mausoleum today. Most of the power brokers, who've run this city's famed Democratic machine for decades, stayed home. The clerks and secretaries, whom they'd placed in jobs, were somber-faced, as if a member of their family had died unexpectedly.

Mayor Michael A. Bilandic, who didn't arrive until midmorning, had been defeated by maverick Jane Byrne in the Democratic primary Tuesday. In all likelihood, big, robust Chicago, "the city with broad shoulders," is going to be run by a woman.

The city was stunned. "Very frankly, no one knows what to do," said Jerome H. Torshen, one of the scores of attorneys who've made a good living representing machine interests.

It was probably the biggest political upset in Chicago history, the first time the Democratic machine, which came to power in 1931, had ever lost a mayoral primary.

The machine wasn't destroyed. But it was damaged badly, left embarrassed and demoralized. It will probably live on. "You don't think because one person in a family dies, the whole family dies," said Alderman Wito Marzullo, one of the machine's staunchest field generals.

But the reading here was the machine, which the late Richard Daley ran with an iron hand for a quarter of a century, would probably never be the same. During her campaign, Byrne, 44, pledged to clean out the top layer of machine patronage appointees at City Hall and redistribute power.

"We'll take some steps to end corruption and cronyism," said Donald Rose, her chief campaign adviser. "We'll knock off the more oppressive aspects of machine politics and open up the process. The power of the old ward basses will diminish. City Council will become more independent."

The great irony was that the person who put together the coalition of blacks, lakeshore liberals and others angry over the condition of city services and insider deals to oust the machine was not any of a half dozen longtime machine critics, but Jane Byrne, a one-time Daley loyalist.

Byrne was Daley's right-hand woman for more than a decade, a trusted and publicity-wise adviser, a confidante who never challenged him in public. He named her commissioner of consumer sales, and cochairman of the Cook County Democratic Party, the base of his fabled organization.

This gave solace to some power-brokers today. "Jane is a pro in this business. She's not some starry-eyed independent" said Alderman Roman Pucinski, a former congressman. "She worked with Daley. She knows the system and how it works."

Byrne, a former schoolteacher, didn't criticize Daley during her campaign. Instead, she capitalized on her ties to him, frequently quoting him as describing her as "one of the most competent women I've met."

Her chief complaint was that Bilandic didn't run the city -- or the machine -- as well as Daley had.

Snow was the catalyst for her election. Until record amounts of it began falling on New Year's Eve, everyone here thought Byrne would get cloubbered, and Bilandic, a bland corporation lawyer from Daley's old Bridgeport neighborhood, would win reelection by a record margin.

The snow strangled the city for weeks. Streets went unplowed. Garbage wasn't picked up. City buses and trains broke down. Until last week, Bilandic insisted that everything was okay. Byrne countered, saying, "The city that works doesn't."

"The bottom line is that it was a protest vote," said Pucinski. "People couldn't forget waiting three of four hours for trains and buses that never came."

But the snow was symbolic of deeper unrest and decay in the Democratic machine, which had grown old, arrogant and corrupt. A $90,000 nobid, insider contract that Bilandic authorized for a party loyalist to develop a snow-removal plan that didn't work brought this home as years of earlier scandals had not.

Chicago's establishment, however, stood by Bilandic, with the media endorsing his candidacy and business and lobor puring more than $1 million into his campaign. Byrne's campaign raised $100,000 most donated by the candidate, the daughter of a retired steel company executive.

"People got fed up and said we don't care what the establishment says," Illinois Gov. Jim Thompson, a Republican, commented. "We're just fed up with the leadership we've had."

The election came as Chicago was experiencing its first real thaw of the winter. The machine, which had counted on a low turnout, found more voters coming to the polls than had two years ago, when Bilandic won the right to complete Daley's term.

"The machine got out its vote, the people it could count on," said Milton Rakove, a University of Illinois professor who has specialized in studying the Democratic organization. "But people came out of the woodwork. People showed up to vote that precinct captains hadn't seen in 20 years."

Byrne carried 29 of the city's 50 wards. Her greatest strength came from black areas on the south and west sides, liberal lakefront wards and the white, middle-class northwest.

She will face Wallace Johnson, 52, who beat Raymond Wardingley, a cabdriver and actor who goes by the professional name of Spanky the Clown, in the Republican primary. A Republican hasn't won a mayor's race here in more than 50 years.

Byrne gave only vague clues during her campaign as to what kind of mayor she might make. Her largely media-oriented campaign centered on attacks on Bilandichs administration.

Whatever she might do as mayor is likely to be in marked contrast to Daley, Bilandic and a string of mayors from the Bridgeport neighborhood going back to Edward J. Kelly, who took office in 1935. She comes from the more affluent, northwestern part of the city.

She was married to a pilot killed in the Korean War, and got her start in politics campaigning for John F. Kennedy in 1960. A picture of Kennedy holding her daughter is one of her prized possessions.

Last spring, she married Jay McMullen, a tough-talking reporter for The Chicago Sun-Times who covered City Hall for the now-defunct Chicago Daily News fro 23 years.

Their romance and the favorable stories McMullen wrote about her were long a subject of controversy in Chicago journalistic circles. When writer Eleanor Randolph wuestioned him about it for an article in Esquire magazine, he said, "I was never ashamed of dating her... She told me more stories than I told her."

As Democratic ward bosses licked their wounds today, the jockeying for position in the Democratic organization had already begun. There was speculation that some bosses might mount a write-in effort on behalf of some other party loyalist, a move emdorsed by several powerful businessmen; that Johnson might be pursuaded to drop out of the race and be replaced by former governor Richard B. Ogilvie (a possibility Oglive dismissed); or that warfare might break out in the organization.

But several key party operatives said the bosses would eventually coalesce around Byrne and she would reach an accommodation with them.

"We have a weak-mayor, strong-city-council form of government here; she's going to need them to govern," said Rakove.

In any event, the rough-and-tumble world of Chicago politics may never be the same. "The is liek the Rock of Gilbtaltar falling into the ocean," said Sen. Charles H. Percy (R-Ill.).