The roughly 60,000 members of the union’s Local 226 rarely pay out of pocket for routine medical care. They can undergo surgery without receiving a hefty surprise bill months later. They can visit the same one-stop medical clinic for urgent care, vision, dental and the pharmacy. The clinic was a regular stop for many of the 2020 candidates.

So one way to understand why the leadership of the Culinary Union is fighting so hard against Medicare-for-all proposals is to look back to the 1990s.

The Frontier, one of the first casinos on what is now simply known as the Strip, had recently been sold to new owners. The Western-themed casino was popular for made-from-scratch baked goods and food.

Gloria Hernandez knew it best for something else: Working there meant she could become a member of the Culinary Union, which would give her medical benefits that were far better than what her husband had through his job.

“You knew immediately that when you started working there that you would get health insurance because this was a union hotel,” Ms. Hernandez said. She knew what it was like to be a member of a union in Mexico, where she was part of the government workers’ union.