Bernie Sanders first touched down in California 10 months ago, and close to 28,000 people filled the Los Angeles Memorial Sports Arena to see him. Just two staffers made the trip. There was something dreamlike about the crowd, and something promising, too.

“By December, when we were looking down the road, California stuck out as a place to compete,” said Sanders’s campaign manager, Jeff Weaver, in an interview.

Today, Sanders travels around California in a caravan of SUVs and campaign buses. The Secret Service guards his hotel rooms and scans the lines where people wait up to six hours to hear the Vermont senator speak. And at long last, his crowds look just like the electorate of the state he is trying to win — young and racially diverse — and they howl with approval after every sentence of a speech that has hardly changed since Iowa.

Sanders is within striking range of a victory in the nation’s largest state thanks to an early decision to play here and a long campaign to convert nonwhite voters that has taken root in ways that it did not in states that front-runner Hillary Clinton won. The principal reason? Young Latinos and Asian Americans, who have registered in huge numbers here in part to oppose Donald Trump and who seem to be coalescing around Sanders.

For nearly two decades, Asian Americans have been the fastest-growing minority in the United States. Their political participation has historically been low, but some like the Vietnamese American community in Orange County, Calif., are actively working to change that. (Alice Li/The Washington Post)

It may be too late for Sanders. He could win California on Tuesday and still effectively lose the nomination the same day, when five other states will also hold primaries and caucuses. And the campaign worries that Clinton’s virtually insurmountable delegate lead could spur television networks to call the race early and depress late-in-the-day turnout on the West Coast.

But in the Sanders stump speech, and in his interactions with voters, there are clues to how he broke through with nonwhite voters. Immigration is now an issue of morality and workers’ dignity; gone are the days when, in sync with some labor leaders, he said that only people such as David and Charles Koch wanted “open borders.” At a Thursday rally in Modesto, Sanders promised to legalize workers by executive order if Congress did not pass “comprehensive” reform.

“Today, there are 11 million undocumented people in this country, and when you are a worker, and when you are undocumented, you get cheated and you get exploited every single day,” he said. “What your employer can do to you if you are an undocumented worker is a disgrace.”

A day earlier, at a forum for Asian American and Pacific Islander voters in Palo Alto, Sanders traded the microphone with activists who raised specific concerns about racism and job security. As he has long done at forums like this, Sanders pivoted with every answer to talk about what he sees as the country’s larger systemic problems.

But that changed when one voter brought up immigration. She asked Sanders about the “2 million-plus” people deported under the Obama administration and about deportations to come. He started his answer with a story about his parents, immigrants from Poland. Then he described his visit to Friendship Park, outside San Diego along the U.S.-Mexican border, one of the events meant to penetrate Spanish-speaking media.

“Anyone been there?” he asked. “It’s a beautiful park, right on the ocean. At that park, there is a fence — a very heavily screened fence — and as I understand it, on weekends, for a few hours, people from both sides of the border can get through the border and talk to each other.”

The room was cramped and hot, with the few open doors doing little to air it out. Sanders did not usually get this personal.

The Fix's Chris Cillizza explains why the June 7 California primary isn't quite the showdown between Bernie Sanders and Hillary Clinton that it's being portrayed as. (Peter Stevenson/The Washington Post)

“Literally, because of the nature of the screen — which is very, very tight — the only physical contact that husbands and wives and children can have is literally putting their pinkies through their fence,” he said. “No hugging. No kissing. That’s the kind of contact they have. And what a tragedy that is.”

Unique opportunity

Since the start of the primary season, Sanders has struggled to earn the support of minorities. The main barrier has been black voters, who overwhelmingly rejected the self-described democratic socialist and handed Clinton her still-strong delegate lead in a string of Southern states. Sanders had hoped to do better with Latinos, but his ability to do so seemed shaky after he lost the Texas primary to Clinton in March.

But California offered a unique opportunity. According to a January 2016 study by the Pew Research Center based on 2014 Census data, eligible voters who are Hispanic skew younger in California than elsewhere in the country and make up a larger slice of the state’s Democratic electorate. As another Pew study from 2011 noted, the average age of Latinos born in California was just 18; the average age of white Californians was 44.

There was also hope for Sanders in polling. A Field Poll of the Democratic race in May 2015 put his overall support among likely Democratic voters at 5 percent. By the end of the year, he had climbed to 35 percent overall and to 32 percent among nonwhites.

“That was even though he’d barely campaigned in California,” said Weaver, the campaign manager. “We hadn’t even advertised here. There was just a tremendous movement with Latino voters.”

The Clinton campaign watched this happen all year, and at key moments, like Nevada’s caucuses and Illinois’s close primary, it appeared to hold off the tide. In 2008, Clinton won California’s Latino voters by a 35-point margin over Barack Obama. Among Latinos younger than 30, she won by 30 points.

Yet in this week’s final pre-primary Field Poll, Clinton led among Latinos by just four points. The Sanders campaign believes he has progressively sliced into her numbers by winning landslide support from younger voters, including Latinos.

Sanders sees these gains as evidence that early losses among nonwhite voters were tricks of the front-loaded Southern campaign schedule. In California, he proved that nonwhite voters could be won over if they simply learned who he was. In a telephone interview Thursday, he said his message is now resonating more with minority voters not because he’s doing much differently but because of a greater familiarity with him.

“Let me give you my prediction,” he said of his performance in California. “If there is a record-breaking turnout, I think we will win by big numbers.”

Age split

Sanders tipped his hand early when he tapped Arturo Carmona to reach out to Latinos. While Clinton’s Latino allies came from the party’s establishment, Carmona is the former head of Presente.org, a network of liberal Latinos who have pressured Obama to take more direct action on immigration.

“We focused on three things in California: Bernie barnstorming the state, outreach to new voters and campaigning heavily among the Latino community,” said Robert Becker, who served as the campaign’s state director in Iowa and Michigan before decamping to come here. “The last poll has shown we’re currently winning there, and that’s not an accident. We’ve put a heavy emphasis in holding conversations with those communities.”

In the first six months of this year, 1.8 million new California voters were registered. Latino registration was up by 123 percent compared with the same period in 2012. The rise of Donald Trump propelled that increase, but Sanders seemed to reap the benefits.

“We’re doing very well with Latinos, in general, and very, very well with younger Latinos,” Sanders told Rolling Stone last week. “What’s been very interesting is that the demographic splits have been less white, black and Latino than they have been on age.”

The support has become impossible to miss. Last week at Sanders’s rally in Ventura, some voters wore T-shirts portraying a young Sanders wincing as police wrest him from a civil rights protest. The sound system, cycling through the usual mix of revolution-centric songs by Pearl Jam and Tracy Chapman, added Latin hits including “La Gozadera” and “Madre Tierra (Oye).”

One voter, Guadalupe Potocacetpl, 35, showed up in the “brown beret” gear of a Chicano nationalist group. He had protested Trump at a Phoenix rally and started having conversations with fellow alienated activists who had jumped aboard with Bernie.

“I met a lot of Bernie supporters, and I liked every single reason they were supporting him,” he said. “At one point, I wasn’t even going to vote because of the outcome of what Obama did — the deportations, the promises that didn’t come through. But then I saw Bernie, and he gave me a little bit of hope again.”

Not far away, brothers John and Brian Meza, 22 and 19, were talking about why they had come to Bernie and why their elders had not.

“I started finding news about Bernie on social media and finding out about Hillary the same way — what she’d said, whether she had changed her mind,” Brian Meza said. “The older people are getting their news from TV, so they don’t see that.”

Sanders has not ignored television. He was on the California airwaves, to the tune of $1.5 million, before Clinton was. More importantly, three months before the primary, his campaign shelled out to broadcast a short film called “Tenemos Familias” on Univision. It told the story of Florida tomato pickers — an issue that Sanders had discovered while in his first Senate term and which he had promoted from his Washington perch.

The ad did not make much of a dent in Florida, but the Sanders campaign could not focus on the state to the same extent it could California. At the end of April, Sanders earned “is it over?” headlines when early-state staff members were fired. But the plan was always to consolidate in California.

“I think you see on an overall basis that he does much better when he has been able to focus on a single state,” Weaver said. “You can build on the rallies in single states, versus in multiple states where the impact is diluted.”

Scott Clement, Emily Guskin and John Wagner in Washington contributed to this report.