In the opening moments of Congress’s first-ever hearing on Medicare-for-all, House Rules Committee Chairman Jim McGovern (D-Mass.) hit on a theme that already has begun to dominate the 2020 Democratic primary season: “Health care is a right for all,” he said, “not a privilege for the lucky few.”

That mantra, which he and others invoked on Tuesday, is political ammunition for liberals’ crusade to convert the U.S. health-care system into a single-payer model. The language casts a redesign, intended to guarantee all Americans access to care by enlarging the government’s role, as a moral imperative.

The most poignant presence during the day-long hearing was that of Ady Barkan, a 35-year-old activist dying of amyotrophic lateral sclerosis, a neurological disease with no cure, who appeared weak and sweaty in a wheelchair and delivered his testimony through a computer because his diaphragm no longer allows him to speak.

“The ugly truth is this: Health care is not treated as a human right in the United States of America,” said Barkan, who testified that his care costs $9,000 a month beyond what his private insurance covers, prompting him to resort to GoFundMe campaigns. “On the day we are born and on the day we die, and on so many days in between, all of us need medical care. And yet in this country, the wealthiest in the history of human civilization, we do not have an effective or fair or rational system for delivering that care.”

But if the talk of rights bolsters liberals’ health-care agenda, it remains polarizing to politicians, policy experts and voters elsewhere on the ideological spectrum. The disagreement makes the United States an outlier among developed nations, almost all of which long ago embraced the value of health care as a human right.

A Pew Research Center survey in September found that 60 percent of respondents said it is the government’s responsibility to ensure that all Americans have health coverage — a marked increase from about a decade ago when the country was more evenly divided. But the partisan differences are stark, with 49 percent of Democrats saying the government should run a single national insurance program but only 12 percent of Republicans agreeing with that idea.

Rep. Tom Cole (Okla.), the ranking Republican on the committee, called the Medicare-for-all measure introduced by Rep. Pramila Jayapal (D-Wash.) “a radical bill,” saying Democrats have “not told us how much this massive new program would cost, who would pay for it and how much taxes would have to go up.”

That dispute was part of the subtext that played out in a small House hearing room as congressional proponents of Medicare-for-all put forth their moral, political and economic case. The hearing offered single-payer proponents their moments in the sun without necessarily moving legislation closer to becoming law. On Tuesday, Ways and Means Committee Chairman Richard E. Neal (D-Mass.) said he also would schedule a hearing.

House Speaker Nancy Pelosi (D-Calif.), a single-payer skeptic, has not committed to other procedural steps that would lead to a floor vote on Medicare-for-all. Even if the measure were to pass the House, it would have virtually no chance of prevailing in the Republican-controlled Senate.

The legislation, introduced two months ago by Jayapal with about 100 co-sponsors, lies at one end of the debate among Democrats over whether the best way to improve health care is to tinker with the Affordable Care Act or to fundamentally restructure the way care is paid for.

Even among Medicare-for-all proponents, there is disagreement about the role for private insurance companies. Some, such as Jayapal and Sen. Bernie Sanders (I-Vt.), contend that private insurance should be eliminated; others suggest that public and private insurance could coexist.

Under Jayapal’s measure, consumers would contribute nothing toward their medical bills, and even long-term care would be covered. Her legislation does not predict how much the new system would cost, leaving it to the secretary of the Department of Health and Human Services to come up with an annual budget.

The Congressional Budget Office is scheduled to release a report on Wednesday on the costs of single-payer coverage.

For an issue that can arouse considerable passion, Democratic and Republican lawmakers and the witnesses maintained a respectful tone. A New York City emergency room doctor and single-payer advocate, Farzon Nahvi, told of patients who walked out of his hospital because they could not afford the care they needed.

Another Democratic witness, Doris Browne, a cancer specialist and retired colonel in the Army Medical Corpsfocused on the need for equitable care for people of all incomes, races and ethnicities. “It doesn’t matter what you call it — Medicare-for-all, universal coverage, single payer — the care must be the same” for everyone, she said.

A Republican witness, economist Charles Blahous of the conservative Mercatus Center at George Mason University, said his analysis of earlier Medicare-for-all legislation estimated it would add $32 trillion to $39 trillion to federal health-care expenditures. But he agreed with Democrats that most, if not all, of that would be offset by the elimination of private health plans.

Among advocates with different views of how to design Medicare-for-all, the idea of health care as a right was a unifying thread.

The idea has a lineage that goes back almost a century: In his 1944 State of the Union address, President Franklin D. Roosevelt called on Congress to adopt a second Bill of Rights that guaranteed Americans economic security, including “the right to adequate medical care and the opportunity to achieve and enjoy good health.”

Roosevelt died the following year, his goal unrealized, but his widow, Eleanor Roosevelt, was a force behind the United Nations’ adoption in 1948 of a Universal Declaration of Human Rights, which said that everyone has the right to adequate medical care. That declaration was the foundation for a 1966 International Covenant on Civil and Political Rights, which said that people should be assured “medical service and medical attention in the event of sickness.”

More than a decade later, President Jimmy Carter signed the covenant, but the United States never joined the nearly 170 countries, including most democracies, that ratified it.

In the 2008 presidential campaign, then-Sen. Barack Obama (D-Ill.) said health care should be “a right for every American.” He was not thinking of Medicare-for-all. He favored federal subsidies to help working- and middle-class people afford private health plans — an idea central to the Affordable Care Act, which a Democratic Congress passed in 2010, and which helped millions of Americans gain insurance but stopped short of universal coverage.

But the idea of expanding Medicare, the popular federal insurance for older Americans, to everyone in the country goes back at least four decades.

As McGovern, the rules chairman, pointed out, Tuesday’s hearing is Congress’s first on legislation called Medicare-for-all. But the late senator Edward M. Kennedy (D-Mass.) convened hearings around the country in 1971 to explore a single-payer plan financed through payroll taxes.

Conservative health-policy specialists contend that, if the government were saddled with the responsibility to provide universal health care — the implication if health care and health were defined as a rightit would be difficult to draw the line about where that should stop. Should it be responsible for providing housing, nutritious food, clean air and other factors known to enhance health?

On the other hand, Don Berwick, a former acting director of the federal Centers for Medicare and Medicaid Services who ran unsuccessfully for Massachusetts governor on a single-payer platform, said the United States “is a unicorn” compared with other developed countries, where the right to health care “isn’t even a question anymore.”