The former officer, exasperated at the increasing use of force to quell the unrest, quit in July after 11 years.

Now she is among scores of new faces vying for office Sunday in citywide elections that have become a referendum on public support for the protests, which have disrupted life for more than five months.

"Some residents still call me a rogue cop but there are others who tell me to keep it up as they want a change this year," said the 36-year-old Yau, who faces a tough battle against an incumbent who has served the constituency for years.

The election for the 452 seats on the city's 18 district councils usually gets little attention but this year has shaped up as a pivotal battleground for protesters anxious to seize the ballot box to legitimize their cause.

For the first time, all the seats are contested in Hong Kong's only fully democratic elections. The pro-democracy opposition hopes to win a decisive victory on the back of public anger against the government and police.

"The election this time serves as a political barometer. The pro-democracy camp certainly wants the results to demonstrate that its cause enjoys the support of the people to show to the world and to the Chinese leadership," said Joseph Cheng, a pro-democracy political commentator.

Those under 36, the backbone of protesters, account for about a quarter of 4.1 million voters — nearly 60% of the city's population.

A drubbing for the pro-establishment camp that dominates the councils would embarrass the city's government and nullify Beijing's narrative that a minority of radical separatists colluded with foreign "black hands" and don't enjoy majority support, he said.

Pro-government candidates concede they are the underdogs but are urging voters to choose stability over violence.

Calvin Sze To, 29, said citizens will need to choose if they "want a stable government or continue to make a mess in Hong Kong." No matter the outcome, he said the government has to look into ways to heal society wounds.

Cheung Ka Yan, a 26-year-old accountant, said she jumped into the fray because many young people who support free elections for the city's leader and legislature — one of the protesters' key demands — decry violence.

"You cannot win universal suffrage by committing arson, killing people and hurling bricks and gas bombs. We must be rational and take one step at a time to realize this goal," she said.

The poll has ripple effects in higher-level elections. The winning camp gets to elect 117 representatives to the 1,200-member panel that picks the city's leader. The pro-democracy camp has some 300 supporters on the panel, so another 117 seats would greatly expand its influence, though still be far short of a majority.

Beijing has recently said it would tighten its control over the selection of Hong Kong's chief executive, though it has not said how.

"The Chinese leadership has indicated that it will retain its hard line and it is unlikely that Beiing will make concessions to a mass movement. It is very concerned of the demonstration effect in mainland China," Cheng said.

Prominent activist Joshua Wong, a leader in 2014 protests for universal suffrage, was the only candidate barred from running on grounds that his party advocates independence.

Police will be deployed to tighten security at dozens of polling stations across the city that will stay open for 15 hours Sunday. Some stations have been moved away from university campuses that turned into combat zones with protesters shooting flaming arrows and petrol bombs in intense clashes last week.

The unrest started in June over a now-abandoned extradition bill that would send criminal suspects to mainland China for trials and is seen as an erosion of freedoms promised to the former British colony when it returned to Chinese control in 1997. It has since morphed into an anti-China movement with demands for universal suffrage and an independent probe on police conduct.

"I cannot accept the fact that tear gas is fired everywhere and police brutality is getting worse. I made the right choice to quit," Yau said while campaigning on a recent afternoon in the upscale Causeway Bay shopping area.

Graffiti across some walls in the city agree that "the ballot is stronger than the bullet."