But Tom Steyer, a former hedge fund manager, was in a close third place and told supporters in San Francisco that he was “going to wait until every ballot is counted.”

“We’re going to give democracy time to work,” he added.

In California’s primary, candidates of all parties run on the same ballot and the top two finishers, regardless of party, advance to the November election. It’s the first time since California began using the top-two primary system in 2012 that a governor’s race has been this close, making it possible that two Democrats could advance to compete for the state’s top office.

Many Californians were uncertain about whom to back for governor and waited until the last minute to cast their ballots, which was expected to slow the tally of final results. The initial election results reflect ballots that were cast early in the voting period. Republicans returned ballots at a faster pace than Democrats did, so the early results were expected to favor Republican candidates, including Mr. Hilton.

The election marked the end of dominance by a cadre of San Francisco Democrats who have wielded enormous influence on California politics for decades. Gov. Gavin Newsom is termed out of office. Representative Nancy Pelosi is retiring. Neither of them endorsed a candidate for governor, and the volatile race to replace Mr. Newsom revealed a fading of dynastic power among California Democrats.

It was the most wide-open contest for governor that California has seen since the 1990s because it lacked heavyweights, and did not have a clear favorite at the start.

It began with 10 competitive candidates. By the final month, the leading Democrats were Mr. Steyer and Mr. Becerra as well as Katie Porter, a former congresswoman; Matt Mahan, the mayor of San Jose; and Antonio Villaraigosa, a former mayor of Los Angeles. The main Republicans were Mr. Hilton and Chad Bianco, the Riverside County sheriff.

Because no one built a commanding lead, California’s nonpartisan primary system drew intense scrutiny, and voters and endorsers become strategic in their decision-making.

Earlier in the year, voters were so uninspired by the Democratic candidates that polls showed there was potential for two Republicans to emerge as the winners in the primary.

Most of the candidates promised to address California’s high cost of living. They proposed various solutions, including cutting taxes, building more homes and providing more government services.

But their policy ideas were often overshadowed by unpredictable twists in the contest.

Democratic leaders initially began to coalesce behind Eric Swalwell, a Bay Area congressman, largely because they feared their party could be shut out of the general election if their voters didn’t gravitate toward one front-runner.

But just as Mr. Swalwell was heading toward the front of the pack in April, multiple women accused him of sexual assault and misconduct, prompting him to drop out of the race and resign from Congress.

Mr. Becerra, who at one point had poll numbers so low that he was excluded from a planned debate, saw a surge of support after Mr. Swalwell’s collapse. To many establishment Democrats, Mr. Becerra seemed a relatively safe choice, with decades of government experience. He was a former congressman and statewide official and had served as secretary of health and human services under President Joseph R. Biden Jr. In mere weeks, he went from being virtually out of the race to the new Democratic front-runner.

“The underdog stayed in the fight,” Mr. Becerra said Tuesday night.

Republican support, which had been split between Mr. Hilton and Mr. Bianco, began to solidify behind Mr. Hilton after he received President Trump’s endorsement. That reduced the likelihood of two Republicans advancing from the primary but then led to a new statistical possibility: that two Democrats might win.

In the campaign’s final weeks, polls showed a close three-way race among Mr. Becerra, Mr. Hilton and Mr. Steyer. Mr. Steyer spent more than $216 million of his personal fortune on his campaign and said his wealth freed him from the influence of corporate interests that supported Mr. Becerra.

Oil companies, real estate interests, tech giants, electric utilities, health care businesses and other interest groups collectively poured about $54 million into supporting Mr. Becerra and opposing Mr. Steyer. Mr. Steyer ran an anti-establishment campaign promising to break up utility companies, pursue single-payer health care and raise taxes on corporations and commercial property.

Mr. Steyer’s closing argument framed the primary as a choice between his populist campaign and that of a corporate Democrat, Mr. Becerra. One of the most counterintuitive developments was the way in which labor unions and Democratic Socialists got behind the billionaire, Mr. Steyer.

Our Revolution, the group Senator Bernie Sanders founded to fight “the billionaire class,” endorsed Mr. Steyer. He also won endorsements from a nurses union that backs single-payer health care and a powerful teachers union that wants to raise taxes.

Mr. Becerra portrayed the contest as pitting a billionaire who had never held elected office against an experienced government leader.

As California’s attorney general during the first Trump administration, Mr. Becerra filed more than 100 lawsuits against the federal government over environmental, immigration and health care policies. Before that, as a congressman representing Los Angeles for two decades, he worked with Representative Nancy Pelosi to pass the Affordable Care Act.

But Mr. Becerra’s Biden administration credentials were marred by accusations that he had demonstrated weak leadership during the Covid pandemic and mismanaged the government’s response to an influx of migrant children crossing the southern border. Mr. Biden did not make an endorsement in the race.

Mr. Becerra was also dogged by a corruption scandal in which two of his top aides pleaded guilty to skimming money from an old campaign account that belonged to him.

Mr. Hilton, who became an American citizen five years ago, campaigned on traditional Republican messages, pledging to reduce taxes and regulations. He echoed Mr. Trump’s rhetoric alleging fraud in Democratic-controlled states and made a campaign stop at the state track and field championships to speak out against a transgender athlete’s participation.

Mr. Hilton acknowledged that there was little he could do to restrict abortion access in California because voters had enshrined reproductive rights in the state constitution. But he has said that, as governor, he would extradite a California doctor who had been indicted in Louisiana for mailing abortion pills across state lines.

Maeve Reston contributed reporting from Los Angeles. Lisa Bonos contributed reporting from San Francisco.