NINGBO, China » A victory by protesters against the expansion of a chemical plant proves the new rule in China: The authoritarian government is scared of middle-class rebellion and will give in if the demonstrators’ aims are limited and not openly political.

It’s far from a revolution. China’s nascent middle class, the product of the past decade’s economic boom, is looking for better government, not a different one. They’re especially concerned about issues like health, education and property values and often resist the growth-at-all-costs model Beijing has pushed.

The past week’s chemical-plant protests reached an unruly crescendo over the weekend, when thousands of people marched through prosperous Ningbo city, clashing with police at times. The city government gave in Sunday and agreed to halt the plant’s expansion.

Even so, the protesters did not back down, staying outside city government offices hours after the concession. About 200 protesters, many of them retirees, returned today to make sure the government keeps its word on the oil and ethylene refinery run by a subsidiary of Sinopec, the state-owned petrochemical giant.

"In yesterday’s protest, the ordinary people let their voices be heard," a 40-year-old businessman who would give only his surname, Bao, said on the protest line today. Government officials, he said, "should say they are completely canceling the project. They should state clearly that they will stop doing these projects in Ningbo and the rest of China."

The protest in Ningbo — a centuries-old trading center of tree-lined streets and canals south of Shanghai now surrounded by industrial development zones — was well-timed. It came a few weeks before a transfer of power in the ruling Communist Party, and Beijing wants calm nationwide so as not to detract from the leadership transition.

Given that pressure and the fact that many Ningbo officials also have middle-class concerns about air pollution and other quality-of-life issues, the local government found it easier to back off, Peking University sociologist Liu Neng said.

"The government would need lots of courage to insist on keeping this project. The cost would be too high if the protest escalated to another level," Liu said. "Since the 18th party congress is around the corner, it is very important to maintain stability."

The protests underscore the challenge the incoming leaders face in governing an increasingly wealthy — and wired — population who are growing more assertive about issues they care about. Democratic movements in places like South Korea and Taiwan started with the middle class, and in Taiwan’s case environmental issues featured prominently.

It’s not the first time the government blinked in the face of middle-class protesters.

In the past five years, officials in the northeastern port of Dalian and the southeastern port of Xiamen have relented on plans to operate or build petrochemical plants after large protests. In Xiamen’s case, worries about declining property values figured as much as health issues.

In 2009, when Beijing ordered computer owners nationwide to install software that supposedly blocked pornography but that people feared was a back door to snooping, a national outcry forced it to back down.

Dalian, Xiamen and Ningbo are among the better-off cities in China. The treatment protesters there received has been gentler than the beatings and large-scale arrests often given to rowdy rural and working-class protesters. Those tend to be larger and more violent, and are seen as more of a direct challenge to the party, which supposedly represents the proletariat.

The recent protests across China against Japan’s move to nationalize some islands in the East China Sea were rare cases in which the government tacitly allowed broader demonstrations.

Even among middle-class protesters, officials are not caving in to all demands. In Ningbo’s case, the government did not heed protesters’ demands for the mayor, Liu Qi, to step down, or for police to release at least seven protesters who refused to heed police orders to leave the area around the government offices.

In the compromises of recent years, the outlines of an unspoken protest compact have emerged: Keep the demonstrations peaceful and focus largely on local issues, and the backlash will be minimal.

The crowds in the Ningbo protests carried smartphones and had mobile Internet connections. Though they often displayed a large dose of skepticism about the party’s official rhetoric, they also urged fellow protesters to stay calm and not fight back against police. The government calibrated its response carefully.

After police tried to thwart the Ningbo protesters on Friday night and scuffles ensued, the government backed off. But the clashes angered the public and seemed to galvanize more participants. Police let the protesters gather and shout for hours, positioning hundreds of riot and military police in the city government compound but at first only sporadically deploying them. They let protesters march through the city’s busy downtown without incident.

By appealing for peaceful protests, the Ningbo demonstrations attracted thousands of participants, said the writer and prominent social commentator Murong Xuecun, the pen name of author Hao Qun.

"That’s a safer way to protest," he said. "If China wants to move toward democracy using a gentle approach it will depend on the middle class."

Associated Press researcher Flora Ji in Beijing contributed to this report.