The Democratic Party in Hong Kong was for decades the city’s largest opposition party. It led protests demanding universal suffrage. Its lawmakers sparred with officials in the legislature about China’s encroachment on the region.

It was born in the 1990s of an audacious hope: that opposition politicians and activists could pressure Hong Kong’s iron-fisted rulers in Beijing to fulfill their promise of expanding democratic freedoms for the city of several million people.

On a rising wave of demands for democracy, the party grew to more than 1,000 members at its height in 2008. Its effort to maintain a moderate stance drew criticism, including from within its own ranks, from those seeking to push harder against Beijing. Yet moderation could not save the party’s leaders from being caught in the dragnet as China tightened its control over Hong Kong.

Now it is disbanding, one more casualty in Beijing’s suppression of Hong Kong’s once-vibrant political opposition.

Its leaders have been arrested and imprisoned on national security charges. Its members are effectively barred from running for local office, and routinely face harassment and threats. Raising money is hard.

“We have not achieved what we set out to do,” Fred Li, a founding member of the party who was not part of the most recent leadership, said in an interview, referring to democratization under Chinese rule. “Without money or resources, we can’t even survive ourselves.”

The party said Sunday that it held a preliminary vote and 90 percent of the roughly 110 members in attendance voted to authorize its leaders to dissolve the party. (The party plans to call another vote in the coming months before it disbands officially.)

Its chairman, Lo Kin-hei, had publicly indicated earlier that the political environment was too challenging to survive, but declined to go into details. Veteran party members like Mr. Li said that Chinese officials or their intermediaries had urged them to disband.

Other smaller pro-democracy parties and civic groups have closed since Beijing in 2020 imposed a national security law giving the authorities sweeping powers to quash opposition, part of a crackdown on free expression more generally. Even a polling group, the Public Opinion Research Institute, said in February that it would suspend all self-funded research after the national security police repeatedly detained the institute’s director for questioning. Critics of the Hong Kong government have been denied entry to the city, including a British lawmaker who tried to visit her newborn grandson this week.

The Democratic Party was established in the twilight of Hong Kong’s days as a British colony, as the city prepared to return to Chinese rule in 1997.

The party’s founders, Martin Lee, a legislator, and Szeto Wah, a union leader, led protests against the Communist Party after it sent troops to crush pro-democracy protests around Tiananmen Square in Beijing in 1989. They co-founded a political group that evolved in 1994 into the Democratic Party.

The Democratic Party sought to hold leaders accountable to two promises enshrined in treaties signed by Britain and China and outlined in the Basic Law, Hong Kong’s mini-Constitution: that the city would retain a high degree of autonomy, and that it would eventually hold direct elections for its top leader.

“They tried to present to people in power: This is what you promised us, so you have to honor it,” said Victoria Hui, a political scientist at the University of Notre Dame, who drafted speeches for Mr. Lee in the early 1990s. “For so long, they took for granted that those words would protect us.”

The party became a thorn in Beijing’s side. Mr. Lee traveled abroad to press Western leaders to hold the Communist Party in check, prompting Beijing to brand him a traitor. His party organized protests to oppose security laws in 2003, eventually forcing the ouster of Tung Chee-hwa, the city’s unpopular leader.

But public discontent rose over unemployment, high housing prices and rising competition for jobs in Hong Kong. The political system was seen as dominated by the city’s business and social elite, and demands grew for greater democracy.

The Democratic Party became a target of criticism at times, including in 2010 when it negotiated with Beijing officials on a plan to expand the number of directly elected seats in the legislature. Other opposition lawmakers rejected the measure, saying it fell short of real democracy. The move also divided the party, leading many to quit.

Despite growing calls for democratic elections, Beijing did not give Hong Kong greater public participation in the election of its leader. People occupied neighborhoods in Hong Kong for about 10 weeks in 2014 in a protest called the Umbrella Movement.

Inside the party, a younger generation began to push back against the old guard, arguing more action was needed, along with talks. The party, which had been steadily losing votes, successfully fielded a crop of new candidates in 2016 including Ted Hui, Lam Cheuk-ting and Roy Kwong, expanding its foothold in the legislature.

Mr. Hui, who was a lawmaker until 2020, said that in the past decade, the party’s nonconfrontational approach began to encounter a more impatient public. “It was a difficult balance walking a moderate path within a radicalizing society, while also needing to get tougher,” he said in an interview.

The party was caught between conflicting political forces. “Their relatively moderate position didn’t really effectively improve the relationship between Hong Kong and Beijing over the past decade,” Ma Ngok, an associate professor of government at the Chinese University of Hong Kong, said in an interview. “As younger people became more radical, the party’s influence has been on the decline.”

A major challenge came during 2019, when months of anti-government protests engulfed the city. Initially marches were family friendly, but descended into violence, with protesters throwing Molotov cocktails. Though the party had long advocated for peaceful protest, its leaders, seeking to maintain unity, hesitated to disavow the violent tactics of some protesters. Younger members of the party tried to mediate between protesters and the police.

After the pro-democracy camp held an unofficial primary in 2020, two weeks after Beijing imposed the security law, the authorities targeted the candidates who had taken part. Many Democratic Party members and leaders were swept up in mass arrests months later. Four former lawmakers from the party were convicted under national security charges and imprisoned. The government has also offered a bounty for the arrest of Mr. Hui, who fled Hong Kong in 2021 and lives in Australia.

No Democratic Party members have held elected office since Beijing imposed a drastic overhaul of the city’s political system in 2021, requiring candidates running for the local legislature and district councils to be “patriots” vetted by Beijing.

For a few years the Democratic Party held on, despite severe constraints. It sought to provide pro bono legal services for the public and to comment on current affairs and on government policies.

“In spite of the fact that we have no position anywhere, people continue to trust in us, and they come to us,” said Emily Lau, a veteran member and a former chairwoman of the party. “But still, under the circumstances, when people get arrested and so on, I think our members are very brave.”

When former Representative Barbara Lee announced that she would run for mayor of Oakland, Calif., many considered her victory to be a sure thing.

After all, Ms. Lee had represented the city for more than a quarter-century in Congress and in the State Legislature before that. She gained national fame as a progressive lawmaker who was the only member of Congress to reject the use of force after the Sept. 11 attacks, reasoning that it gave the president too much war authority.

To Ms. Lee’s supporters, her return home was seen as a worthy bookend to her career, with a chance to rescue her hometown from its doldrums and political decay. Oakland, a city of 436,000 residents across the bay from San Francisco, has suffered mightily since the pandemic as it has faced soaring crime rates, the departure of its last major sports team and a yawning budget deficit.

The city had a sudden vacancy at the top because voters ousted Mayor Sheng Thao in November, a sign of their frustrations with the city’s direction and with a dark legal cloud over Ms. Thao.

But Ms. Lee, 78, is no longer considered a shoo-in to win Tuesday’s election.

Loren Taylor, a former Oakland City Council member, has gained traction with voters as a moderate candidate who has pledged to fix potholes, reduce crime and shorten 911 response times.

Ms. Lee is still considered the heavy favorite in the field of 10 candidates. But Mr. Taylor, 47, recently surpassed her in fund-raising and landed the endorsement of the editorial board at The San Francisco Chronicle. “Oakland is broken,” Mr. Taylor often says on the campaign trail, a message that has resonated with some voters.

Mr. Taylor’s momentum serves as the latest indication that residents in the liberal San Francisco Bay Area are giving greater emphasis on quality-of-life concerns than before.

Voters in November ousted Pamela Price, the progressive district attorney in Oakland and surrounding Alameda County, who had sought reductions in criminal sentencing. In San Francisco, voters last year elected a business-friendly moderate, Daniel Lurie, as their new mayor. The City Council in nearby Fremont, Calif., this year tried to make it a crime to help people living on the streets.

Mr. Taylor described himself a “pragmatic progressive.”

“We have to focus on results, and we can’t just be resting on ideological sort of values, regardless of the impact on people’s lives,” he said. “I think that’s where, frankly, the far left progressive movement has gone astray.”

Just over a year ago, Ms. Lee was campaigning to replace Dianne Feinstein in the Senate, which was the reason she did not run for a 14th full term in the House. In that race, she trailed in fund-raising and endorsements but drew support from progressives for her willingness to buck the establishment. She finished a distant fourth.

Back in Oakland, Ms. Lee has had a role reversal: She is now the establishment candidate.

Over the past three months, Ms. Lee has secured a diverse slate of endorsements from high-profile groups and leaders, including the Oakland Chamber of Commerce; labor unions; state legislators; four former Oakland mayors; and seven of the eight members of the Oakland City Council. Jim Ross, a political consultant in Oakland who is not involved in the race, called it “the most impressive group of endorsements” in a California mayor’s race that he could recall.

Much of her plan in the first 100 days doesn’t prescribe solutions but calls for collaboration. She wants to bring together police and business leaders. She hopes to convene C.E.O.s. She wants to appoint a task force of good government experts to modernize city government.

“Because I have a history of bringing different sides of views and issues together to find common ground, that is exactly what I will do as mayor,” she said.

In Oakland, Ms. Lee and Mr. Taylor do not have material differences in their stated values, and they seem to agree on what the city’s biggest problems are. If there is a contrast, it is that Mr. Taylor has more eye-catching specifics.

He has called for bringing city employees back to the office four days a week. He wants to publicize how long each building permit has been delayed through a “shot clock.”

Mr. Taylor’s recent traction seems to have come from his positioning as a pragmatist who could usher in a new generation of Democrats, as well as change a city in disarray.

“Under any normal circumstances, the people of Oakland would be throwing rose petals at Barbara Lee’s feet, but these aren’t normal times,” said Dan Schnur, a political analyst who teaches at the University of California, Berkeley. “The level of resentment and anger is off the charts.”

Though San Francisco has drawn the most national attention since the pandemic for its property crimes, fentanyl deaths and store closures, Oakland has suffered far more. Long regarded as a less expensive, gritty alternative to San Francisco, the city has lost population along with its optimism in recent years.

In November, voters ousted Ms. Thao less than two years after she took office. While the city’s woes made her vulnerable, an F.B.I. raid on her home last summer as part of a corruption investigation made political survival difficult. Then in January, Ms. Thao was indicted on federal charges of conspiracy and bribery.

The political fallout has persisted even after her departure. City documents that were under investigation by the F.B.I. included one note written by Ms. Thao’s chief of staff that referred to Black people as “tokens” that could be used to ward off the recall threat last year, The San Francisco Chronicle reported this month. Soon after the revelation, the aide, Leigh Hanson, was fired from the same chief of staff role she was performing for the interim mayor.

Whoever wins Tuesday’s election will finish out Ms. Thao’s term through the end of 2026.

Mr. Taylor, who narrowly lost a mayoral race in 2022 to Ms. Thao, has positioned himself as a challenger who will bring the kind of shake-up that Oakland needs by navigating the city bureaucracy and politics with expertise from years on the City Council.

“I’ve been on the ground working through our most difficult challenges with the community, whereas Congresswoman Lee has been in Washington, D.C., for the past 30 years,” he said.

But Ms. Lee said her congressional experience would be an advantage as mayor, vowing to fight to get the city the resources it needs from her connections. “It’s important to have a mayor who’s going to fight for whatever there is left with the federal government,” she said.

When pressed about the competitive nature of the race, Ms. Lee directed the conversation toward what she would do rather than address Mr. Taylor specifically. She thought Oakland residents were still more aligned with her than her opponent’s moderate approach.

Ms. Lee said that she thinks her goals — investing more in public safety, reducing poverty, building more affordable housing — remain in line with voters here.

“In Oakland,” she said, “we have Oakland values.”

But there are factors also working against Ms. Lee. In a special election such as this one, fewer voters turn out, and they tend to skew more moderate.

Voters in Oakland are divided. Some say the city needs the stability of a longtime member of Congress like Ms. Lee after the recent turmoil at City Hall. Others believe that Mr. Taylor, as the change candidate, would set the city on a better path.

Whitney Johnson, a dentist who has lived in Oakland for decades, said he was primarily concerned with crime. At night, he walks in the middle of his street instead of on the sidewalk, he said, so he can avoid being cornered by someone who might mug him.

Holding a cup of coffee and walking his dog through the city’s charming Rockridge neighborhood Thursday, he pointed to shop after shop where he had seen storefronts shattered or cars parked with their windows smashed.

He said he admired Ms. Lee’s record in Congress, but planned to vote for Mr. Taylor for one simple reason: “He’s different.”

David Moore, 62, said he cast his mail-in vote last week for Ms. Lee because she’s a trusted voice. He said that he doesn’t know if any mayor will have the power to change Oakland’s problems, but he hopes Ms. Lee can guide the city with an experienced hand.

Mr. Moore had one suggestion for Ms. Lee, should she win.

“Don’t have the F.B.I. come after you,” he said.