LOS ANGELES — At an auditorium here one evening this week, Atticus Tyagi stepped onstage with a canvas bag nearly as large as he is, bearing the name of his “Gammy” — Senator Elizabeth Warren — and the elementary schooler calmly chose raffle tickets to determine who in the audience of thousands would have a chance to ask his grandmother, Ms. Warren, a question.
Last month, donors dined on salmon and kale salad while listening to former Vice President Joseph R. Biden Jr. in Brentwood. Two days later, some of the same guests returned to the same home to listen to a similar speech from their own senator, Kamala Harris.
Ms. Harris may be California’s homegrown candidate, but the other Democratic candidates are clearly not conceding the state as her turf.
In July, Mayor Pete Buttigieg of South Bend, Ind., spoke in a San Francisco warehouse and Senator Bernie Sanders pressed the case for “Medicare for all” in Hollywood and Little Tokyo. This week, Senator Cory Booker showed up in South Los Angeles for a discussion on gun violence. And this weekend, more than a dozen presidential candidates will speak to the party faithful in San Francisco for a Democratic National Committee meeting.
With a deep base of wealthy donors, California has long been treated as a political A.T.M. In 2020 it will become something else too: An early voting state. Or closer to one than it has been since 2008. As soon as next February, voters here can begin casting early ballots to determine how the state’s nearly 500 Democratic delegates — more than any other state in the country — will be divvied up in the nominating contest. The primary itself is March 3, Super Tuesday, and because California is not a winner-take-all state, campaigns are eager to compete for any number of delegates from the state.
“I think we love being the popular girl or boy at the dance right now,” said Eric Garcetti, the mayor of Los Angeles who considered his own presidential bid and has longstanding relationships with several candidates. Mr. Garcetti said that candidates have long come to California to raise money, but not to court voters. Or, in school dance terms: “Historically, people want us to pay for the dance but nobody wants to dance with us. Now, suddenly we’re able to hit the floor.”
Since Ms. Harris announced her candidacy with a large rally in Oakland, her campaign has put considerable effort into lining up endorsements from elected officials at every level up and down the state, including Gov. Gavin Newsom. She also continues to raise millions from her local supporters, holding half a dozen fund-raisers in the span of one July weekend.
Ian Sams, a spokesman for the Harris campaign, said that it views California as a huge opportunity for Ms. Harris, and a place where she does have an advantage.
But the campaign has also made clear that it needs to spend significant money to defend that advantage. If Ms. Harris were to lose on her home turf, it would most likely spell the end of her candidacy. This week, the campaign announced it had hired several new staff members to work in Los Angeles and Oakland.
The campaign has also been focused on earning statewide endorsements, though some of the state’s most prominent officials, including Mr. Garcetti and former Gov. Jerry Brown, have so far not backed a single candidate.
“Of course we have familiarity, respect and affection for our own senator, but we are too big and too diverse of a state to move with one parochial mind,” Mr. Garcetti said in an interview.
Mr. Brown, who remains one of the most popular politicians in the state, said that candidates should do more than “the obverse to the rightward tilt” from Republicans, no matter how angry Democratic voters may seem. Mr. Brown, who lost his own bid for president, declined to comment on any of the candidates specifically, including Ms. Harris, whom he has known for decades.
“Trump is not popular here, that is an understatement, but after a while, when it’s only attacks on Trump, that doesn’t feel like there’s much substance there,” Mr. Brown said in an interview. “It’s a very thin debate right now, as I see it, and for many Californians, and I’m sure many Americans, it’s not all that interesting.”
While Ms. Harris has consistently been one of the top candidates in several polls of California voters, Mr. Biden has repeatedly surpassed her, and Mr. Sanders and Ms. Warren are each within a few points.
Officials from several campaigns said they were just beginning to hire staff members in California, but planned to open offices in multiple regions of the state, acknowledging that what works in Silicon Valley, where voters skew wealthy and white, may be very different from the Central Valley, which is heavily Latino and more conservative. At a Warren event, a campaign staff member actively recruited Spanish-speaking volunteers.
While the Warren campaign has so far hired just one staff member to oversee the state, officials say they have amassed thousands of volunteers here and Ms. Warren plans to hold events in the state almost monthly. Her children and grandchildren live in Los Angeles, which leads to some travel efficiency: After the state Democratic convention in San Francisco last month, Ms. Warren flew south to attend her grandson’s high school graduation.
Mr. Sanders also has a sizable infrastructure to fall back on from the 2016 Democratic primary, when he captured 46 percent of the vote in California. The campaign recently hired a statewide coordinator who will oversee an expansive operation.
His California supporters are a receptive group — hundreds of people lined up in scorching afternoon heat to attend a health care town hall he held in Little Tokyo, just east of downtown Los Angeles.
“All the issues we wish everyone was talking about, that some other candidates are starting to talk about now, he’s been talking about them forever,” said Alex Perez, a 42-year-old military veteran who lives in the San Fernando Valley and had come to see Mr. Sanders speak. “Our own senator, I like her, yes, but she is playing catch up.”
Mr. Perez’s attitude — appreciative of Senator Harris, but enthusiastic about other options — was a sentiment that dozens of voters expressed, to varying degrees, during a summer of plentiful opportunities to see candidates. They also noted that they were trying to make sense of how Ms. Harris’s positions had shifted over her 15 years in public office, and what she really believed. But mostly, they were excited to get a small taste of what Iowa voters have gotten for years: A chance to see the presidential hopefuls for themselves. And they did have several chances.
On one busy day in July, Mr. Sanders taped an appearance on Jimmy Kimmel and then headed to the Montalban Theater in Hollywood, where he took the stage after the crowd warmed up to a thumping D.J. set.
Across town, Mr. Buttigieg was holding his own fund-raiser with celebrity hosts that included Ellen DeGeneres and Chelsea Handler. A day earlier, Mr. Buttigieg attracted a couple of hundred Bay Area supporters to an industrial section of San Francisco, for a fund-raiser that featured a panel discussion on diversity and the tech industry. There, he received huge applause after promising to solve homelessness, one of the most pressing and vexing problems in California. When he spoke of homes in South Bend selling for $40,000, he was met with roaring laughter.
Whether California Democrats are looking for a moderate would-be peacemaker or an unapologetic liberal may prove to be the central question of the primary here.
Carolina Rojas, 44, was eager to bring her 9-year-old daughter to Ms. Warren’s event on Wednesday in Los Angeles. It was just the second day of fourth grade for Valentina, who stood in line for more than an hour to ask Ms. Warren about global warming and how she handled self-doubt. Ms. Rojas was leaning toward Ms. Warren, and newly focused on how important this election will be. “I’ve really come to see that every issue I care about is connected and we really need big changes,” she said. “El Paso showed us you can’t really tease out gun control from immigration and from racism.”
Congressman Harley Rouda, a Democrat who captured a long-held Republican seat last year and has become a vocal supporter of impeaching President Trump, said he was most focused on a candidate who could beat Mr. Trump in swing states, and worried that candidates were taking positions that would alienate voters.
“I think it’s very important that we not go so far to the left that we lose the strength we achieved in 2018 — that was not because we made blue districts bluer, it was because we turned red districts blue,” he said, adding that he was unsure whether he would endorse anyone in the primary. “We did that in a place like Orange County because people want to see a pragmatic approach, not more bickering.”