Maria Vallardes came to the door in slippered feet, a pomeranian yipping behind her. Standing on her porch with a clipboard and an earnest smile was Ricardo Alonzo Ugalde, a volunteer with the Bernie Sanders campaign assigned to canvas in this corner of east Los Angeles, the heart of the Latino community.

“Buenas tardes, señora,” he greeted Vallardes before launching into his pitch. The California primary election was Tuesday – did she plan to vote? She did. And was she a registered Democrat? She laughed, as if the question was preposterous. Of course, the 65-year-old told him in Spanish. “Do you think I would vote for Donald Trump?”

She invited him inside to hear more. When he left, her ballot was sealed, along with her support for Sanders.

“That’s about as good as it could possibly go,” said Alonzo Ugalde, a 35-year-old engineer who knocks doors and phone banks for the campaign in his spare time.

If Sanders becomes the Democratic nominee this time around, it will likely be with the support of neighborhoods like the one Alonzo Ugalde canvassed on the Sunday before Super Tuesday: racially diverse, working-class communities across the south and the midwest where voters feel left out or left behind. His campaign says that outreach was key to Sanders victory in Nevada, where the 78-year-old senator won support from more than 50% of Hispanic voters in a seven-way contest, according to entrance polls.

“Brown people love Bernie Sanders,” said Chuck Rocha, the colorful architect of Sanders’ campaign strategy to mobilize Latino voters. “We realized that too late in 2016. So we started building where we left off.”

Outreach began almost immediately after Sanders launched his campaign last year. In speeches, the candidate has complemented his focus on economic inequality with calls for racial justice. And, seeking to deepen Sanders connection with nonwhite voters, his campaign has highlighted aspects of his personal story as the son of a Polish immigrant who came to America without any money or knowledge of the English language.

Rocha, who wears a cowboy hat and speaks with a Texas drawl, said the campaign learned from 2016 that it needed not only to invest heavily but to invest early in Latino communities. And that begins with hiring. Rocha boasts that the campaign has no “Latino department”. Instead, Latinos fill prominent, decision-making roles at every level. Under the banner of “Unidos con Bernie”, Rocha said the campaign has demonstrated its “cultural competency” with Latinos. That effort has included hosting “Tamales for Tío Bernie”, screening the Disney film Coco and sponsoring a soccer tournament.

Super Tuesday will be the most consequential test yet of Latino support for Sanders. California and Texas, the biggest delegate prizes of the primary election, both have large Latino electorates.

Surveys show Sanders with a commanding lead among Latinos in both states, but Joe Biden’s victory in South Carolina has revived his campaign and will boost his standing with voters of color across the country.

Biden, who will hold a primary night event in Los Angeles, has polled well with older Latinos, though they make up a smaller share of the electorate. Meanwhile, Bloomberg, who has poured hundreds of millions of dollars of his own fortune into the Super Tuesday states, has also been targeting Latinos with Spanish-language ads and mailers.

Strong performances with Latinos in California, Texas and Colorado could prove decisive on Tuesday and propel Sanders into the next series of contests, which includes Arizona and Florida.

In California, the campaign has 105 staff members and 23 field offices statewide, which Rafael Návar, Sanders’ California state director and a native of East LA, said are mostly in “heavily Latino” and “working-class” neighborhoods.

Sanders visited the state for the opening of a field office in Coachella, located in the same unit where the labor leader and civil rights activist Cesar Chavez organized on behalf of the United Farm Workers of America in the 1960s.

“You had not had somebody running for president visit the city of Coachella since John F Kennedy,” Návar said.

Bernie Sanders and Alexandria Ocasio-Cortez during a campaign rally at Venice Beach in Los Angeles in December. Photograph: Monica Almeida/Reuters

The endorsement of Alexandria Ocasio-Cortez, the 30-year-old Latina congresswoman from New York, solidified Sanders’ standing among young Latinos in particular. At a rally together in Queens, she adorned him with the nickname Tío Bernie, an endearment that has resonated with Latinos who have come to see Sanders as their champion.

“The story of our community is one of constant struggle in America, a struggle to be recognized, and to have full citizenship and full rights,” said Návar, a former labor organizer with the Communications Workers of America. “And so I think there’s a real connection because he’s seen as someone who has always been fighting against overwhelming odds.”

Many young Latino supporters say they are drawn to his promise of Medicare for All and free college tuition. But another major part of his appeal is his ambitious immigration platform. Sanders has also taken some of the most liberal stances on immigration of any Democrat, policies that Latino staff, including some undocumented members of the campaign, helped to shape.

“Latinos are going to the polls with the economy and healthcare in their minds and immigration in their hearts,” Clarissa Martinez de Castro, deputy vice-president of UnidosUS, the largest Latino civil rights and advocacy group in the country.

Sanders has vowed to reverse all of Trump’s executive actions on immigration on “day one”, including ending his “zero-tolerance” policies and restoring the Daca program for young undocumented people Trump’s administration cancelled. He has also promised to place a moratorium on deportations until further review, end raids by Immigration and Customs Enforcement (Ice) and pass comprehensive immigration reform with a pathway to citizenship for some of the nearly 11 million undocumented immigrants in the US.

Even Sanders critics agree his outreach has been impressive. Luis Alvarado, a Los Angeles-based Republican consultant who specializes in Latino voter outreach, praised Rocha’s approach but remains skeptical that Sanders can replicate his early state success.

“Nevada Latinos are mostly blue-collar, worker-class with a family tie to a union,” he said. “Because of that, the messaging of being a Democrat socialist resonates. I don’t see that same formula applying to Latinos in a state like California and Texas.”

Compared with Nevada, Alvarado said there is a broader range of economic and educational attainment among California’s Latino electorate. And Texas Latinos are traditionally more conservative than Latinos in California and Nevada. In 2018, four in 10 Hispanics voted for Texas’s Republican governor, even as Latino turnout in the state drove the “blue wave” that helped Democrats regain the House majority.

The Vermont senator is now the choice of 51% of Latino voters in California, up 13 points since January, according to the final UC Berkeley Institute of Governmental Studies poll of the contest. And an NBC/Marist poll found 46% of Texas Latinos prefer Sanders, more than three times the support earned by his nearest rivals, Biden and Bloomberg.

The Sanders campaign is also courting Latinos in North Carolina and Virginia, where a rally in Richmond last week drew more than a hundred activists from the local chapter of Casa in Action, an immigrant rights group that endorsed him.

“We are leaving no stone unturned,” Rocha said.

Yet Sanders’ recent praise for certain aspects of the Cuban revolution has alarmed Latinos in Florida, one of the most critical presidential battlegrounds. Democrats and the party quickly condemned the comments but say they fear the impact his nomination would have on the state’s down-ballot candidates.

“Revolución and camarada are not words that should be used in Florida,” said Evelyn Perez-Verdia, a Florida-based Latino issues strategist who is Colombian American.

She said his praise of socialist governments in Latin America risks alienating not only Cuban Americans, many of whom are Republicans, but also Venezuelans, Colombians and Nicaraguans. Among Latinos in Florida, Sanders polls notably behind Biden and Bloomberg.

The campaign does not view Sanders’ remarks as problematic, ascribing the backlash to members of “the Democratic establishment and Republicans who never liked Bernie anyway”, Rocha said. The campaign has announced ad buys in Florida and has already deployed staff to the state, where they are targeting younger progressives who have no memory of the cold war.

“The people we are talking to on the ground there love him,” Rocha said.

Two days before Super Tuesday, the most consequential voting day of the presidential primary, more than 15,000 people poured into a convention hall for a Sanders rally in downtown Los Angeles. Outside sellers hawked “Tío Bernie” T-shirts as street vendors pushed carts that sizzled with bacon-wrapped hotdogs.

Speaking at the rally, Marisa Franco, co-founder of Mijente, a Latinx activist organization, said the complexion of the crowd on Sunday night showed that Sanders’s support among Latinos was “undeniable”.

And why is a 78-year-old senator from one of the whitest states in the country resonating with Latinos, whose median age is 29?

“Real easy,” she said. “Because he’s working for it. Because his platform speaks to our people and because of the concept of palabras” – the consistency of his message.

The senator stepped on stage, and, admiring the size of the crowd, boasted that the establishment was getting “very nervous”.

But there was nothing to fear, he assured them. His political philosophy was simple: “My family cares for your family. Your family cares for my family. We grow together.”

Among those in the crowd was Alonzo Ugalde, the volunteer who spent the afternoon canvassing for Sanders in East LA. By the time polls close on Tuesday, he estimates he will have knocked on 2,500 doors since he began volunteering with the campaign in April 2019.