At a strip mall across the street from the University of Nevada-Las Vegas, several Bernie Sanders volunteers stared at their phones, pretending to be disinterested in politics. Fellow volunteers walked over to them, and pitched the Vermont senator’s solutions to the student debt crisis and rising college tuition costs. Handing over clipboards, they offered volunteer information and urged their pretend-targets to commit to supporting Bernie. Then both groups traded roles, and those who played the distracted UNLV students practiced delivering Sanders’ plans for reform.

This was mid-January, and Sanders was already leading the organizing race in Nevada, the third presidential primary contest of the 2020 calendar.

Nevada voters are headed to the polls on 22 February at noon, and the race is a crucial test case for the appeal of the Democratic presidential hopefuls among a diverse coalition of Democrats.

The caucus format of the “first in the west” vote tends to favor the campaign with the strongest ground support. Nevadans who don’t vote early have to arrive at designated caucus precincts by 12pm to stand in their preferred candidate’s corner. Loyalty, in the raucous scene, can be tested. And tensions developed during debates and through paid and unpaid media may be on display. Nevadans working on the Las Vegas Strip who want to vote will be able to step away from their card tables, beverage stations, kitchens and housekeeping carts and join fellow staff in ballrooms reserved to caucus inside the MGM Grand, Bellagio, Wynn and other resorts.

A Las Vegas Review-Journal and AARP Nevada poll released on Friday showed Sanders with 25% support, followed by former vice-president Joe Biden with 18%, Massachusetts senator Elizabeth Warren at 13%, businessman Tom Steyer at 11%, and former South Bend, Indiana, mayor Pete Buttigieg tied with Minnesota senator Amy Klobuchar at 10%.

Bernie Sanders volunteers in front of the campaign office for the University of Nevada-Las Vegas in January. Photograph: Dan Hernandez/The Guardian

In addition to a burgeoning army of volunteers, the Sanders campaign employs 250 people in the silver state, more than double the staff of Pete Buttigieg, the second-largest campaign at 100.

Lourdes Esparza, 38, said she volunteers for Sanders because her mother and grandmother can’t afford adequate healthcare and are forced to ration medicine and pass on doctor’s appointments to avoid co-pays. Esparza canvasses door-to-door despite also working weekdays at a teachers union and weekends hostessing at a restaurant. “‘How much is it going to cost?’ shouldn’t be the first words that come out of my grandmother’s mouth when she gets sick,” Esparza said.

Austreberto Hernandez, a 26-year-old immigrant rights advocate, said he will support Sanders for his “deliberate” approach to progressivism. “I feel like Bernie Sanders normalized the idea of a pathway to citizenship for undocumented immigrants [in 2015] because he said it a million times on the campaign trail.”

“All that stuff – universal healthcare, a $15 minimum wage – Bernie just pounded to death and now they’ve become household names.”

Joe Biden volunteers attend a precinct captain training. Photograph: Dan Hernandez/The Guardian

Late last month, at a Joe Biden campaign field office in North Las Vegas, a dozen supporters had gathered to be trained as precinct captains. The strip mall space had aviator sunglasses painted on the wall across from a “Restore” “Rebuild” and “Unite” slogan, key tenets of the former vice-president’s nostalgia-driven campaign.

Having suffered embarrassing losses in Iowa and New Hampshire, Biden’s narrative of electability desperately needs reviving in Nevada. The former vice-president polls well in communities of color. Both Iowa and New Hampshire – where he finished in fourth and fifth places, respectively – are over 90% white. But whether Nevada’s diverse Democratic base will rescue his claim to viability is as uncertain as splitting aces on a cold blackjack table.

Lucy, a retired letter carrier said she likes Biden’s “overall good view of the American people”. “His empathy is something we need to bring back to our communities,” she said.

A woman named Maria defended Biden’s controversial touchy-feeliness as proof of his compassion, while adding: “He knows what to do when he gets to the White House. He has dignity, and he is a family man.”

Allan, wearing a military veteran’s hat, said he liked Biden “because I think he can beat Trump”. Those sentiments were repeated. But some supporters admitted to having wavered to and from other candidates.

“I’m one of those people who’s indecisive, but not really indecisive because nobody jumps out as the most whatever,” said DeeAnn Bear, a retired teacher. “Like this gentleman, I want someone who’s able to beat Trump. Someone who has knowledge, and is honest, and doesn’t just act like a five-year-old having a temper tantrum.”

“I’ve come to realize that no matter how good your ideas are, you’re never going to convince everybody,” said Linda Ogleby, an activist since the 1960s. “Even if Medicare for All is the ultimate great idea, it’s going to take, like water, slowly to get there.”

One Biden supporter said he liked the vice-president ‘because I think he can beat Trump’. But some supporters admitted to having wavered to and from other candidates. Photograph: Dan Hernandez/The Guardian

Law school student Justin Williamson saw Elizabeth Warren as a kindred spirit. Williamson has worked with vulnerable populations throughout his career. He was a licensed foster parent, and served as a court-appointed special advocate to look out for the best interests of children in abuse and neglect cases. Before that, he cared for people in residential and inpatient psychiatric treatment.

“One of the appeals of Warren is that that’s the focus of her work: let’s do the most we can for people who have the least advantage. We have a lot of systemic things that need to be fixed.”

He likes that Warren approaches policy in an “overtly nerdy but evidence-based way”. Alluding to the Massachusetts senator’s career as a law professor, Williamson noted: “She’s like, ‘I have done this research and looked at this problem and originally I started from this position, and was like, what is wrong with these people? Then I studied it and realized the system is set up to screw the people with the least ability to deal with it.’”

Reflecting on what makes the state unique, Williamson said, “Nevada represents a lot of what is going on in the country that often gets missed. It’s got a lot of almost shadow populations. They’re people that don’t have a ton of money, power, representation, so they don’t get seen or heard from. People living on the fringes, where housing is inconsistent. Access to healthcare is also a huge deficit in the state. Just all these social things are more acute here, and I do think among those who are caucusing there is greater contact with that than there might be in other places.”

On the sideline of the Martin Luther King Day parade, Rich Gilroy said that a year ago he would have voted for Joe Biden. But then he saw Pete Buttigieg speak at a Las Vegas coffee shop, and felt moved by the former mayor’s candidacy. When they shook hands afterward, Gilroy told the former mayor that as a gay man, he never thought he’d see this day come.

Rich Gilroy said that a year ago he would have voted for Joe Biden. Now he’s supporting Pete Buttigieg. Photograph: Dan Hernandez/The Guardian

“That was my initial attraction,” Gilroy said, “but I think I support him now not just because he’s gay – and openly gay – but because he’s such an adult. He’s what I consider a pragmatic progressive. He’s smart, he’s charismatic. When he speaks, he inspires me. He lifts my spirits.”

Gilroy compared Buttigieg’s message and delivery to that of Barack Obama in 2008 for the way it instills him with hope. “I think Buttigieg is the polar opposite of what we have in the White House now,” he added.

“No matter who gets the nomination I’m going to be out volunteering and working for that candidate.”

With days to go until the caucus, the political fervor in Nevada has only heated up. In every election cycle in the state, requisite attention is paid to the maneuvers of the powerful Culinary Union, which represents more than 60,000 resort industry employees, most of whom work in Las Vegas.

The union declined to endorse a candidate this go around, but issued subtle anti-endorsements through a flyer for members that stated: “We have fought for 85 years to protect our health care. Why would we let politicians take it away?”

The implied rebuke of Sanders’ and Warren’s healthcare plans, by which private insurance would be eliminated, suggested that the union’s work negotiating top-tier medical coverage for members and their families would be squandered.

A second warning via email said Sanders’ proposal would “End Culinary Healthcare”. Some Sanders supporters responded with hostile messages and other forms of harassment that the campaign disavowed and condemned.

Bernie Sanders volunteers practice pitching the Vermont senator’s policy proposals to voters. Photograph: Dan Hernandez/The Guardian

The kerfuffle was convenient in a way, drawing maximum attention to the union’s opposition to Medicare for All. But its impact remains to be seen, as the union’s clout in the Democratic primary is less impactful than in general elections.

In 2008, Culinary endorsed then Senator Barack Obama in the Democratic caucus but Hillary Clinton still won a majority of the contests on the Strip and claimed Nevada’s popular vote. (In a sign of things to come, she still earned fewer delegates.) In 2016, the union stayed neutral as Clinton narrowly defeated Sanders, a result furiously disputed at the state convention during delegate allocation. A chair was raised as if to be thrown, and death threats ensued.

Not to be left out of the potential chaos and chicanery, Donald Trump is encouraging his supporters to take part in the process to support the “weakest” Democrat (even though registered Republicans can’t vote in the Democratic caucus). And on their end, “Never Trump” Republicans have established a not-for-profit organization to identify disaffected conservatives and independents willing to register as Democrats and support moderate candidates.

“Anti-Trump conservative voters have a clear interest in the Democrats nominating a standard bearer who is both ideologically tolerable – even if there are major differences on policy – and more likely to defeat the president and allow the Republican party to move beyond Donald Trump,” the announcement said.

• This article was updated on 19 February 2020 to amend a description of Sanders supporters.