Small employers in particular, and their workers, are struggling.

“Health insurance in the United States is incredibly prohibitive for small businesses,” said Shalin Madan, the founder of a small investment advisory firm in Florida. He is not required to provide health insurance to his workers, because his business is too small and he outsources much of the work.

A policy for his own family, he said, runs about $2,000 a month ($24,000 per year), with a $13,000 deductible. “I’m out $37,000 before I see a return on investment, if you will,” Mr. Madan said.

A recent Wall Street Journal/NBC News poll found that a majority of registered voters, 56 percent, are opposed to the idea of a government-run system like Medicare-for-all that would replace private insurance. But Mr. Madan said the current system results in a schism between those who have good employer coverage and those who do not.

“I had phenomenal health insurance being employed,” said Mr. Madan of his time working for a larger corporation.

One of Senator Elizabeth Warren’s applause lines on the Democratic presidential campaign trail is that no one likes their insurance company. But employer coverage “isn’t monolithic,” said Mr. Altman.

While some people, usually higher-paid professionals or union members, enjoy generous coverage from their job, people making $25,000 or less — about 36 million Americans — are the most likely to be priced out of coverage, he said.

People who work at companies where a large share of the employees are low-wage workers pay an average of $7,000 annually for a family plan, according to the survey, about $1,000 more than those working at companies made up of better-paid workers.