Irene Aguilar knew for a long time that America's healthcare system was broken. She had worked as a doctor in one of Colorado's "safety net" hospitals, where the uninsured and seriously ill go for care. Some of her patients were there because they had lost insurance after being laid off, others lost insurance because they divorced a spouse whose job had been providing it. Who qualified for insurance-covered care could seem cruel and nonsensical. The "classic example," she told me, were diabetics who wound up on dialysis because they couldn't afford the medications that would let them manage their condition.

The solution was pretty obvious to Aguilar and many of the people working alongside her: A "single-payer" system, also called "Medicare for all," where the government provides health insurance to everyone and pays hospitals and doctors for services directly. Not only would that have made Colorado's population at large less vulnerable to the whims of employers and the insurance market, it would have saved the state an estimated $1.4 billion by cutting down on the overhead and waste inherent in a system where for-profit insurance companies serve as middlemen.

But Aguilar didn't understand the politics of healthcare fully until 2007, when she was invited to participate in a Colorado state commission studying healthcare reform. The mother of a disabled daughter, Aguilar was assigned to a subgroup focused on the problems facing "vulnerable populations." Not used to that kind of committee work, she found the sheer amount of talking overwhelming, almost "painful," she told me. But she's proud of the conclusions her group reached: Since even the insured can lose health insurance due to unemployment, thrusting them into sudden crisis, everyone in America could accurately be described as "vulnerable." The current system wasn't just failing the sick and needy, it was failing, full stop.

"Once you're on dialysis, you automatically qualify for Medicare. I was furious that I had patients who had worked all their lives and they end up on dialysis and they can't work anymore and we give them full coverage," she said. "It seems so fiscally irresponsible that we didn't help them control diseases and prevent high-cost complications that would lead to premature death—but once they had those complications we paid for them."

"Being politically naive, I thought, Well, this is what the commissioners are going to pick," Aguilar said of the various proposals on the table. "Then I learned about politics of healthcare and healthcare reform."

She went on: "I literally sat behind one of the commissioners [at a meeting with politicians] to make sure that when they made their report to the legislature that they told them there was a plan that covered everybody and saved $1.6 billion, because I was still naive enough to think that would sway them. And one of the legislators said, 'Yeah, but that's the single-payer plan, right?' She said, 'Yeah.' So they said, 'Tell me about the next one.'"

The commission's final report, released in January 2008, didn't exactly deliver on Aguilar's dreams; it suggested the state require residents to buy insurance and give them subsidies to do so, among other things. That proposal resembled the Affordable Care Act, a.k.a. Obamacare, which became federal law a couple years later and was nearly gutted by Republicans in Congress last month.

Aguilar's disappointment in single-payer not being given a fair hearing is familiar to anyone who's converted to the cause of universal, government-provided healthcare in America. People like Aguilar, who was appointed to the Colorado State Senate in 2010, believe healthcare is a right. They point out that United States fails to provide care to many millions of people, resulting in thousands of deaths annually, while spending way more than comparable nations. Expanding Medicare so that it covers everyone is a far simpler, more politically coherent reform than the complicated carrot-and-stick approach of Obamacare; it would also insure a lot more Americans. Sure, taxes would have to go up to pay for this new system. But some economists say people would pay less overall because private insurers spend money on advertising and other expenses the government could ignore.

As Aguilar found out the hard way, the problem facing single-payer advocates is not fighting Republicans—who will probably never support such a dramatic expansion of government in the first place. Instead, it's convincing Democrats. A combination of the insurance lobby's influence, the power of anti-government rhetoric, and many politicians' natural caution has turned single-payer into a political orphan, an impossible dream. But these days, the left wing of the Democratic Party is rising in anger to challenge both Donald Trump and Clinton-esque moderates, unafraid of adopting positions that were once dismissed as "socialist."