SAN FRANCISCO — As they made their way into a breakfast for union members meeting ahead of the California Democratic Party’s annual convention here on Saturday, Sen. Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE (I-Vt.) and former Rep. Beto O’Rourke (D-Texas) braved a boisterous phalanx of supporters backing their hometown hero, Sen. Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (D-Calif.).

“Whose house?” one Harris backer yelled. The rest shouted back: “Kamala’s!”

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Public polls, and the receptions that several other candidates earned before delegates meeting at the Moscone Center, show Harris has work to do to win her home state, the largest prize up for grabs on Super Tuesday.

California has been both a boon and a burden to Harris, who won her Senate seat in 2016. It is the most populous state in the nation, the home of big donors who have funded Harris’s campaign and hundreds of volunteers who can operate the phone banks. But its size and diversity, both geographic and demographic, makes it harder to compete here than in any other state in the country.

No Democrat has ever won the party’s nomination without carrying their own state in the primary process. That puts the pressure on candidates like Sens. Michael Bennet Michael Farrand BennetOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency Next crisis, keep people working and give them raises MORE (D-Colo.), Elizabeth Warren Elizabeth WarrenDimon: Wealth tax 'almost impossible to do' CNN's Don Lemon: 'Blow up the entire system' remark taken out of context Democrats shoot down talk of expanding Supreme Court MORE (D-Mass.), Amy Klobuchar Amy KlobucharSocial media platforms put muscle into National Voter Registration Day Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE (D-Minn.) and Sanders, as well as O’Rourke, former Housing and Urban Development Secretary Julián Castro (D) and former Colorado Gov. John Hickenlooper John HickenlooperCook Political Report shifts Colorado Senate race toward Democrat Willie Nelson playing at virtual fundraiser for Hickenlooper Gardner on court vacancy: Country needs to mourn Ginsburg 'before the politics begin' MORE (D), all of whom will see their home states vote on Super Tuesday.

But none will face stakes as high as those confronting Harris, because carrying California is such a massive and expensive undertaking.

“The great thing about California Democrats and California voters is they make decisions based on issues. They make decisions based on the connection to the relevancy of what you’re talking about and their lives,” Harris told reporters on Saturday. “I am here to earn everyone’s support and I am going to fight to earn it.”

She has earned a mammoth amount of institutional support. Gov. Gavin Newsom Gavin NewsomOVERNIGHT ENERGY: California seeks to sell only electric cars by 2035 | EPA threatens to close New York City office after Trump threats to 'anarchist' cities | House energy package sparks criticism from left and right California seeks to sell only electric cars by 2035 EPA head questions connection of climate change to natural disasters MORE (D), four statewide officeholders and huge majorities of both the Senate and Assembly Democratic caucuses back Harris. The only notable defectors include Sen. Dianne Feinstein Dianne Emiel FeinsteinFeinstein 'surprised and taken aback' by suggestion she's not up for Supreme Court fight Democrats shoot down talk of expanding Supreme Court Biden leads Trump by 12 points among Catholic voters: poll MORE (D), who supports former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE, and state Sen. Henry Stern (D), who backs South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegThe Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice Hillicon Valley: FBI, DHS warn that foreign hackers will likely spread disinformation around election results | Social media platforms put muscle into National Voter Registration Day | Trump to meet with Republican state officials on tech liability shield MORE.

In a state that is notoriously hard to organize, support from local elected officials matters: They serve as on-the-ground mini-organizations that can activate volunteers and chase voters in the weeks leading up to the primary.

“Californians love Kamala Harris,” California Secretary of State Alex Padilla (D) said in an interview. “Her wins as attorney general statewide and her win as a U.S. senator were more than impressive. That’s going to count for a lot.”

Harris is already building her team in the state. The California contingent is being guided by Courtni Pugh, a veteran operative plugged into the essential world of union politics who worked for Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE’s presidential campaign in 2016, when she won California’s primary.

Harris’s consulting team is a California-heavy group led by Ace Smith, Sean Clegg, Laphonza Butler and campaign manager Juan Rodriguez, veterans of the state’s complicated politics and the races that propelled Harris to where she is today. They say the state is not a must-win for any candidate in the field, though Harris insiders acknowledge California is a top priority.

“We have an operation that is chock-full of people who were working on those races,” said one top Harris adviser. “We’re the furthest ahead in our California play in terms of the actual operational mechanics and maneuvering.”

But Harris has work to do among California voters. An April poll conducted by Quinnipiac University shows Biden leading the field in California at 26 percent of the vote. Sanders took 18 percent, virtually tied with Harris’s 17 percent.

Warren, who won the loudest applause at this weekend’s convention and who drew 6,000 supporters to a rally in Oakland, and Buttigieg finished tied for fourth at 7 percent of the vote each.

In interviews with a dozen party strategists, operatives and elected officials here, many said Harris must win California’s March 3 primary if she has any chance of winning the nomination.

“Not only does she have to win in California to get the nomination, she has to win so the long list of politicos here who have endorsed her early don’t have egg on their faces with the voters in California,” said Anthony Reyes, a former top aide to state Senate President Kevin de León. “If they can’t pull this off here it will speak volumes on what direction California voters — a formidable contingent of the Democratic base — want to go in if they end up defying the state’s political establishment.”

California is the largest of 16 prizes available on Super Tuesday, when eight Southern states, two New England states and a smattering of others cast their votes, including American Samoa and Democrats Abroad.

And, in a sense, California is a microcosm of all the other states that will vote that day. It has huge constituencies of African American voters, like Alabama, Georgia and North Carolina. It has Hispanic communities in Los Angeles and the Central Valley as significant to a Democratic primary as Texas’s. It has rural white voters in the north and east, like Minnesota and Vermont, and a core of white liberals in Bay Area cities who resemble the voters who make Massachusetts and Virginia blue and blueish.

It is California’s very size that makes Harris’s challenge all the more complex.

“In a smaller state, she would have a higher profile. Here, she has to compete with car chases and Kardashians,” said John Pitney, a political scientist at Claremont McKenna College and a former spokesman for the Republican National Committee. “Senators can seldom dominate state politics as governors can.”

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Other contenders have shown no deference in Harris’s home state. More than a dozen showed up to address the state convention this weekend.

Democratic rules allow candidates to receive delegates to the national convention by winning, or at least reaching 15 percent of the vote, in individual congressional districts. That requires candidates trying to win the state as a whole to spend heavily on some of the most expensive media markets in the country, and it allows others to go delegate-hunting in more specific areas.

Buttigieg left the convention for a campaign swing through the Central Valley. Sanders held a rally in Pasadena before heading to the convention. Washington Gov. Jay Inslee Jay Robert InsleeBarr asked prosecutors to explore charging Seattle mayor over protest zone: report Bottom line Oregon senator says Trump's blame on 'forest management' for wildfires is 'just a big and devastating lie' MORE (D) held fundraising events in the state, and Montana Gov. Steve Bullock Steve BullockMcConnell locks down key GOP votes in Supreme Court fight Senate Democrats demand White House fire controversial head of public lands agency Pence seeks to boost Daines in critical Montana Senate race MORE (D) will hold his own events there later this week.

Harris’s team acknowledges the challenge ahead, one that will fuse long-term planning with fortuitous short-term timing. Strong performances in early state contests in Iowa and New Hampshire will build energy she — or any candidate — needs to carry into Super Tuesday.

“You’re going to have to have a lot of money, you’re going to have to be polling well, and you’re going to have to be in the news” to win California, the Harris insider said. “We need to be strong and run very competitively in those first few states and go into Super Tuesday with momentum.”