In a different scenario, the governor’s race in California would already have taken shape. Aspiring candidates would have been making appearances around the state. Donors would have begun bankrolling their favorites, and organizations would have started to announce endorsements.

Instead, Kamala Harris came home.

The former vice president, after a stinging defeat in the presidential race last year, has shaken up the 2026 governor’s race by her mere presence in California. Speculation has grown each week since her return from Washington: Will she or won’t she enter the race?

After flying back to Los Angeles last month, Ms. Harris has stood with firefighters in Altadena, greeted evacuees at a Red Cross shelter and toured fire damage in Pacific Palisades. During her most recent stop, she did little to quell speculation.

“I am here, and would be here, regardless of the office I hold, because it is the right thing to do,” Ms. Harris said when reporters pressed her about whether she was running for governor.

The possibility has made it difficult for most other Democrats to move forward, realizing that any calculations they make now would be upended if Ms. Harris entered the race . The 2026 contest to replace Gov. Gavin Newsom, who cannot run again because of term limits, is currently populated by lesser-known aspirants, many of whom likely would step aside if Ms. Harris decided to run.

“She hasn’t frozen the field, but definitely made it icy enough to force everyone to slow down and watch their step,” said Dan Newman, a Democratic strategist who advised Mr. Newsom during his campaigns for governor.

Ms. Harris is weighing whether to run for governor next year, run for president in 2028 or pursue a role outside of elected office, according to a person with knowledge of her deliberations. She has put together an advisory team that includes former White House staff, veteran Democratic strategists, policy experts, a speechwriter and a fund-raiser.

Running for governor might seem to be a step down for someone who served four years as the vice president and was the Democratic nominee for president. But by doing so, Ms. Harris would avoid the competitive slog of a presidential primary and have a strong chance to lead the nation’s most populous state with the help of fellow Democrats who control the legislature. Ms. Harris has won in California every time she’s been on the statewide ballot — as a candidate for president, vice president, senator and attorney general.

By this point eight years ago, the last time California had an open governor’s seat, the major Democratic candidates had fully launched their campaigns and Mr. Newsom had emerged as the front-runner in polls. Though the primary election is still 16 months away, it takes longer in California than elsewhere for candidates to raise money and become known to voters across a vast state with expensive media markets.

So far, the declared Democratic candidates include the lieutenant governor, the schools superintendent, a former mayor of Los Angeles, a former state controller and a former legislative leader. Though they’ve begun to raise money and seek endorsements, they are little-known to voters, making the race an unpredictable free-for-all.

Eleni Kounalakis, the lieutenant governor, was the first to jump into the governor’s race when she declared her candidacy in April 2023. At the time, the possibility that Ms. Harris might enter the race was on few minds.

Because Ms. Kounalakis and Ms. Harris have been friends for more than two decades, it’s difficult to imagine them running against each other. Their friendship dates back to when Ms. Harris was the San Francisco district attorney and Ms. Kounalakis was running her family’s home-building company in the same city, “both young women, trying to navigate the halls of power,” Ms. Kounalakis said in a speech at the Democratic National Convention. Ms. Kounalakis was not available for comment.

While most Democrats are in wait-and-see mode, the prospect of Ms. Harris’s entry seems to have energized some Republicans. Chad Bianco, the sheriff of Riverside County, launched his campaign on Monday. Republican Steve Hilton, a Fox News commentator and former adviser to British Prime Minister David Cameron, who lives in Silicon Valley, is also weighing a run. And Richard Grenell, who has a home in Manhattan Beach, Calif., and is President Trump’s envoy for special missions, said last week that he would consider running for California governor — if Ms. Harris gets into the race.

Such candidates would face long odds in a state that has not elected a Republican to statewide office since 2006, when voters re-elected Arnold Schwarzenegger as governor. But Republicans believe competing against Ms. Harris, especially after her loss to President Trump, could energize their supporters and attract more donations.

“She would be a very enticing opponent to Republicans,” said Matt Shupe, a campaign strategist who is advising Mr. Hilton.

If Ms. Harris does run, it would be a rare move for someone who came so close to the presidency. Only four vice presidents have run for governor, and one dropped out to support another candidate, according to Joel Goldstein, an emeritus law professor at Saint Louis University who has studied the history of vice presidents.

In 1804, Aaron Burr lost his race for governor of New York, an outcome that he blamed on Alexander Hamilton before he shot Mr. Hamilton dead in their famous duel. In 1894, Levi Morton, the vice president under President Benjamin Harrison, won the New York governor’s race.

The most direct parallel, however, was Richard Nixon. In 1960, Mr. Nixon, then the Republican vice president, lost the presidential race to John F. Kennedy. He returned home to Southern California and ran for governor in 1962.

Mr. Nixon adjusted to the parochial nature of a governor’s race and pledged to visit every county in the state, according to news accounts. He signed autographs in the rain in the Sierra Nevada foothills, posed for photos with “coonskin capped” mountain men and played piano for potato farmers near the Oregon border, The Los Angeles Times reported in February 1962.

In the 2026 governor’s race, some prominent Democrats have yet to announce their intentions as Ms. Harris weighs her decision.

Katie Porter, the former congresswoman known for viral moments in which she grilled executives with her whiteboard on Capitol Hill, has made several trips to Sacramento in recent weeks to meet with labor leaders and others who are influential in Democratic politics — indications that she has been laying the groundwork to get in the race. But she also has suggested that she and others would be unlikely to take on Ms. Harris.

“If Vice President Harris were to choose to run, I am certain that that would have a near field-clearing effect on the Democratic side,” Ms. Porter said at a post-election discussion in December.

Another Democratic leader has decided to forego the governor’s race. Rob Bonta, California’s attorney general, had been considering a run but announced this month that he will instead seek re-election as the state’s top lawyer and will support Ms. Harris if she runs for governor.

Not every Democrat would scatter. Two candidates who are positioning themselves as business-friendly moderates said that they will stay in the race even if Ms. Harris jumps in. Antonio Villaraigosa, a former Los Angeles mayor who ran unsuccessfully for governor in 2018 and now works for the cryptocurrency company Coinbase, said that he’s running again because too many Californians are struggling with the cost of living.

“Because nothing has changed for them, nothing has changed for me,” Mr. Villaraigosa said.

Stephen Cloobeck, a real estate developer who has given his campaign $3 million, said Ms. Harris’s time in Washington has left her disconnected from California voters.“I welcome her entering the race if she decides to do that,” he said.

It is not clear when Ms. Harris might make a decision.

Lorena Gonzalez, the president of the California Labor Federation and a former Democratic state lawmaker, said that the prospect of Ms. Harris’s entry has “slowed everything down.”

The labor federation has invited candidates for governor to speak to union members at an event in May to begin considering an endorsement.

“We never thought that would look too early,” Gonzalez said. “But now it seems like it might be.”

In 1962, the last time a vice president came home to run for governor, Mr. Nixon lost to Edmund G. “Pat” Brown, the Democratic incumbent.

It was that defeat that led Mr. Nixon to tell reporters, “You won’t have Nixon to kick around anymore because, gentlemen, this is my last press conference.”

Six years later, he was elected president.

Orlando Mayorquín and Jesus Jiménez contributed reporting. Sheelagh McNeill contributed research.