The debate around a national health care system stretches back more than 100 years in the United States, having been advocated by President Theodore Roosevelt as early as 1912. At the time, many world leaders marveled at the universal health care system demonstrated in Germany as the way of the future. Eight centuries later, then-First Lady Hillary Rodham Clinton would suffer one of the most significant defeats of her political career when her universal health care plan failed to earn enough Democratic votes in the Senate. 

The road toward a true national program has been a rocky one.

The history of single-payer advocacy in the United States is one of internationalism, featuring many faces of opposition, as well as political and literal warfare.

The first major strike against a national health care program in the United States came with the shot heard around the world: When World War I started, "Everything German became tainted politically," according to David Jones, professor of the culture of medicine at Harvard University.

"Since [government-controlled] health care insurance was German, it became bad and anti-American," Jones said in a phone interview.

Only years before the first Red Scare, opponents seized on the depiction of government-run health care as socialist. Organizations including the American Medical Association would also paint single-payer health care as taking freedom away from health professionals and patients, Jones said. The thinking was that a government-run system would force patients to see limited panels of doctors, and doctors would lose their autonomy to an overly bureaucratic system.

"All those things that groups were afraid government would do, private insurers have now done," said Jones, who worked as a psychiatrist.

It would take World War II to popularize the modern system of employer-based health insurance.

The wartime draft took so many employable men out of the economy that the costs of labor skyrocketed. In order to maintain the economy's equilibrium, President Franklin D. Roosevelt issued an executive order that froze wages. This wartime crisis provided a golden opportunity for insurance companies.

"If you were a company, you were now competing for labor, you couldn't raise your salaries because those were under federal caps, so you started to offer benefits: sick days, vacation days, and health insurance," Jones said.

Within a few decades, the usage of private insurance catapulted from 9 percent to 70 percent. The momentum seemed like it would take the United States away from the nonprofit models of insurance in Europe and toward private sector coverage. But employer-based insurance left out two groups: the unemployed, who were often poor, and the elderly, who were retired.

Medicare

Medicare was proposed to cover Americans over 65, and it has proven to be more cost-effective than private insurance.

But in the lead-up to its passage, groups lobbied against the program heavily. The American Medical Association, for instance, hired a young Ronald Reagan to lambaste the program on vinyl as the first step on a slippery slope toward socialism and the loss of American freedom.

Medicare became a model for the future, despite being "red-baited," according to Theodore Brown, author of "Comrades in Health: U.S. Health Internationalists, Abroad and at Home" and a professor of medical humanities at the University of Rochester.

"We do have a single-payer system; it's for a specific age group," Brown said in a phone interview.

The adoption of a Medicare-for-all system has been proposed for decades, with senators such as Ted Kennedy calling for it as early as 1969.

Sen. Bernie Sanders, I-Vt., championed the concept during the Democratic primary.

Today, the opposition to a single-payer system largely comes from economists, who argue that it would be too expensive, and from private insurance companies, which would cease to exist under such a system.

Both Jones and Brown balked at the argument that single-payer health care would make the United States worse off economically.

"You'd be hard-pressed to look at U.S. health care and see what value competition has provided; in comparison to any other industrialized country, we have by far the highest costs, twice the per capita spending of the next highest spending country, and it's pretty difficult to argue that our care is better than Switzerland or France," Jones said.

"We would save enough money by moving to a lower administrative expense that just the money we saved administratively would be enough to pay for all the uninsured people that are currently uninsured," Brown said.

The critiques of the current system come as projections predict that monthly premiums for Obamacare will rise 25 percent on average next year.

The discontent with the system, which is being publicly criticized even by Democrats, coincides with surveys showing that almost two-thirds of Americans support a Medicare-for-all system.

"I think one thing to ask is, 'Are we really now in a new moment [for Medicare-for-all]?' I think there's some evidence to support that," Brown said.

Longtime Sanders supporter Brown said that he believes Sanders' popularity during the Democratic primary is a sign that we may have reached "a turning point."

"That tells us something about what Millennials are willing to consider and maybe be persuaded by that their parents and older generations weren't able to," Brown said.