LAS VEGAS — Barbara Clark walked through the double doors of the Doolittle Community Center in north Las Vegas late Tuesday afternoon still unsure about how to cast her vote.

Clark, 52, a tour bus driver, said she wanted her first-choice candidate in the Nevada Democratic caucuses to be someone who could prevail against President Donald Trump in the general election come November.

So maybe, Clark thought, she should pick a moderate, someone like former Vice President Joe Biden or San Francisco billionaire Tom Steyer.

But then Clark thought of her missing front tooth. It had rotted out about two years ago, and even with her health insurance, the dental procedure to replace it was too costly for the mother of three. She needed that money for bills and rent.

Clark said she believed Vermont Sen. Bernie Sanders and his "Medicare for All" plan could improve her life and the lives of many others. But she was nervous he could be too far left to win in the end.

"It was really tough," Clark said of her choice. "I wasn't sure what to do."

More than 36,000 Nevadans voted early in the state's caucuses, and many of the nearly two dozen voters who spoke to NBC News echoed Clark's concerns. Some chose to cast their vote based on electability. Others said they supported candidates whose positions on key issues matched their own. Overwhelmingly, health care was the most significant issue for voters interviewed at three polling locations in Las Vegas on Tuesday.

It's a topic that made national headlines this month when the Culinary Workers Union, Nevada's largest and most politically influential union, distributed flyers warning that Sanders' push for a single government health care plan would end the union's health plan, according to The Nevada Independent. The organization, which represents 60,000 casino workers in Nevada, including those at most of the hotel resorts on the Las Vegas Strip, feared losing the health insurance plan that the union had fought for decades to acquire for its members.

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During Wednesday night's debate, Sanders stressed that he would never sign a bill that would reduce the Culinary Workers Union's health care benefits. "We will only expand it for them, for every union in America, and for the working class of this country," he said.

The flap did not dissuade Kelly Gray, 42, a member of the union who manages a few local bars in Las Vegas, from casting his vote for Sanders. Gray, who also teaches jiu-jitsu, said he doesn't believe that Medicare for All would harm union workers. Rather, it would make it possible for the Culinary Workers Union to focus more on other issues, like fair wages, he said as he waited in a line Tuesday outside Cardenas Market, an early voting site in east Las Vegas.

A voter checks in on the final day of early voting for the upcoming Nevada Democratic presidential caucuses on Feb. 18 in Las Vegas. Mario Tama / Getty Images

"I feel like they think it's somehow going to take some of their importance away," Gray said of the culinary union. "I know change is scary, but there's so many other issues that they could be working on."

Virgil Green, 54, cast his vote at the Doolittle Community Center for Biden because he said he believes in Biden's promise to improve and protect the Affordable Care Act, former President Barack Obama's signature health care law. Green said his choice was driven by his younger brother's struggles with health care after he left a full-time job in a casino cafe a couple years ago to become an Uber driver. About a year later, Green said his brother, now 41, was diagnosed with a heart condition requiring a pacemaker. While he qualified for Medicaid, some of the procedures and equipment he needed were denied, Green said.

Green, who works in construction, worries that Trump's proposed federal budget, which includes about $1 trillion in cuts to Medicaid and the ACA, would hurt people like his brother.

"All the other candidates are just giving us ideas, but Biden's actually been there and done it," said Green, adding, however, that he believes the single-payer plan proposed by Sanders sounds too good to be true and that he does not understand how it would be funded.

Jackie Wiseman, who works in sales for a local brewery, said affordable and accessible health care has been an issue for her since 2012, when her aunt died of ovarian cancer. Wiseman, 33, said her aunt, who owned a local T-shirt printing business, did not have health insurance before being diagnosed. She said her aunt lost her house and cars, trying to pay for treatments.

Wiseman, who receives health benefits through work, voted for Sanders because of his health care plan. "If my health insurance gets a little worse because of it, it's still worth it if everyone can have health insurance," she said. "I want to pick someone who wants everyone to live happy and healthy lives."

Sanders, who finished first in the New Hampshire primary and virtually tied for first in Iowa's caucuses with Pete Buttigieg, has taken the lead in the national Democratic race, according to an NBC News/Wall Street Journal poll released this week. Heading into the Nevada caucuses, Sanders also led other candidates in the state, with 25 percent support, according to a recent poll by The Las Vegas Review-Journal.

Chris Cruz, 48, said he chose Sanders because of his plan to tax millionaires and billionaires to close the country's wealth gap. Cruz, who works in sales, said he and his wife have sacrificed having children so they could make ends meet.

"The wealthy have to start paying their way and it's long overdue, and he has been saying it for years," Cruz, who voted at the Chinatown Plaza Mall in southwest Las Vegas, said of Sanders.

People wait in line on the final day of early voting for the coming Nevada caucuses in Las Vegas on Tuesday, Feb. 18, 2020. Mario Tama / Getty Images

Some voters said they chose moderate candidates in the hope that they would draw in undecided voters in the general election.

"I just want someone to beat the big, orange assclown," Simon Peck, 55, said after voting for Buttigieg, the former mayor of South Bend, Indiana, and Sen. Amy Klobuchar of Minnesota (early voters in Nevada have the option of selecting up to five candidates in order of preference). Peck said he believed the two would not be as polarizing to moderate voters. "I just really hate seeing the direction this country is going in, and we need someone who can win," he said.

As she held an iPad with the ballot Tuesday afternoon, Clark, the tour bus driver, said she struggled for several minutes with how to vote. She thought about the country's division since Trump had taken office, about how he'd alienated black Americans, like herself, and how badly she wanted him out of office.

She also thought about the affordable housing crisis and friends and relatives unable to afford their rent. Clark thought about the times she had to forgo a doctor's appointment to pay a utility bill.

Then she selected her first choice: Bernie Sanders.

"We really need somebody who cares about the community and wants to help them," she said. "He's been there, he hasn't given up and we need to give him a chance."