The Capitol Hill health care fight sure seemed dead. After Republican proposals to overhaul the Affordable Care Act, also known as Obamacare, failed to pass a Republican-controlled Congress, lawmakers looked poised to move on to other topics, like a tax overhaul. But this week, proposals from both the left and the right are grabbing headlines. (Meanwhile, some members are also wrangling over how they can stabilize Obamacare.)

On Wednesday came a "Medicare for All" bill from Vermont Independent Sen. Bernie Sanders — his attempt to push single-payer health care, long one of his favorite causes.

In a Wednesday op-ed in the New York Times, the former presidential candidate wrote about single-payer health care as a moral issue, giving it his familiar populist framing.

"We remain the only major country on earth that allows chief executives and stockholders in the health care industry to get incredibly rich, while tens of millions of people suffer because they can't get the health care they need," he wrote. "This is not what the United States should be about."

Spoiler: It's not going to pass this Congress. But with 2020 (already) on people's minds, single-payer seems primed to be something Democrats will be talking about for the next few years.

So here's a quick primer on what is in Sanders' bill — and why it matters, despite being dead on arrival.

The basics

Sanders' plan is a "single-payer" plan. That means the government will be the "single payer" on any health expenses. Right now, there are lots and lots of payers in the U.S. health care system — insurance companies, the federal government, states and so on.

"Medicare for All"? Not quite. Sanders calls his plan "Medicare for All," but that's more of a handy slogan than reality, as this plan would greatly expand Medicare and overhaul it — for example, it would greatly expand the type of coverage offered and also eliminate deductibles, copays and premiums. Private insurance companies are also currently a part of the Medicare system. That wouldn't be the case under Sanders' plan.

Phased in over time. The Sanders plan wouldn't extend insurance to all Americans immediately; rather, it would do it over four years (and would, as stated above, greatly change the program). The first year, the Medicare eligibility age would be lowered to 55. That would move to 45 and then to 35 over the following two years, until finally, in the fourth year, everyone would be covered.

Covers all sorts of things. Sanders proposes generous coverage that goes well beyond what Medicare currently covers, and even well beyond what many people's private insurance plans cover. His plan would cover dental and vision care, for example, which are, for the most part, not covered by Medicare.

Payment is unclear. A generous plan that covers all Americans is going to require more revenue. There's no exact plan for how to pay for Sanders' bill, but he did on Wednesday afternoon release a list of potential payment options. Among the proposals: a 7.5 percent payroll tax on employers, a 4 percent individual income tax and an array of taxes on wealthier Americans, as well as corporations. In addition, Sanders' plan says the end of big health insurance-related tax expenditures, like employers' ability to deduct insurance premiums, would save trillions of dollars.

But even with all of those potential revenue-boosters, Sanders may still fall far short of the total amount of money needed to pay for his ambitious program. Altogether, his estimates of how much money his funding mechanisms would generate totals up to around $16 trillion over 10 years. In a 2016 report on his presidential campaign's "Medicare for All" plan, the Urban Institute estimated that the plan would cost $32 trillion over 10 years.

What problems would it solve?

Reducing the number of uninsured. (Duh.) A byproduct of universal health care is that, well, people are universally covered.

Out-of-pocket spending: up or down? This would most likely vary from person to person, according to one health care expert.

"The dollars they're currently paying out of pocket would go down, but government costs would go up substantially," said Linda Blumberg, a senior fellow in health policy at the Urban Institute, a Washington think tank. "So depending on the person's income and the way the program is financed, which is not in this proposal yet, people's taxes are likely to go up substantially."

For some people, the tax increase will exceed what they're saving on out-of-pocket costs — looking at Sanders' proposed taxes, this may apply to high-income people. For other people, the savings could exceed any tax increases.

Health care costs: up or down? It's hard to answer this one, as some aspects of this plan would push costs down, while others would push it up.

"The single-payer, government-run system has the potential to control prices much better than our current system," said Larry Levitt, a senior vice president at the Kaiser Family Foundation. With a simpler system would come lower administrative costs, making health care much more efficient, for example; and the government would negotiate drug prices, bringing health care costs down, as well as the price per service.

On the other hand, getting rid of those out-of-pocket costs has the potential to push overall spending up.

"More people would be covered — and that would drive up spending — and having no deductibles and copays will sound great to patients, but it means that people will be going to the doctor a lot more than they are now, and that will drive spending up," he said.

Supporters of Sen. Bernie Sanders, I-Vt., hold signs Wednesday during an event on health care on Capitol Hill. (Alex Wong/Getty Images)

The politics

This bill will not pass. ... And Sanders knows it, as NPR's Scott Detrow wrote in August. "The whole thing is more about political framing — getting Democrats to the point where this would be a top priority whenever the party is back in power," Detrow wrote.

Political signaling. Sanders' bill is the latest piece of evidence that Democrats are moving further and further to the left on health care. Sanders is an independent who considers himself a "democratic socialist," but he caucuses with the Democrats. His popularity in the 2016 Democratic primary signaled a party willing to move further left.

Sanders didn't win over a single co-sponsor when he introduced a similar measure in 2013. On Wednesday, he had 16, including several other high-profile Democratic senators who are being talked about as potential 2020 presidential candidates, including California's Kamala Harris, Massachusetts' Elizabeth Warren, New Jersey's Cory Booker and New York's Kirsten Gillibrand.

Positioning themselves as proponents of socialized insurance could help Democratic candidates win over some voters in the party's base. Now they each have video for their possible 2020 primary campaign ads, speaking next to Sanders during Wednesday's rollout in support of his bill.

But people on the left disagree on how central single-payer should be to Democrats' messaging going forward.

"A commitment to universal health coverage — bringing in the people currently falling through Obamacare's cracks — should definitely be a litmus test," wrote Paul Krugman in the New York Times in August. "But single-payer, while it has many virtues, isn't the only way to get there."

Single-payer has grown more popular, but polling is tricky. Recent polls have shown that the idea of single-payer has grown more popular in recent years. But as with a lot of issue polling, people's opinions on single-payer are pretty movable, as NPR reported in July. Tell them about the potential for higher taxes, and support for single-payer slips substantially. Tell them about the potential for lower administrative costs, and support grows.

Republicans appear eager to do that. On Wednesday they were already branding "Berniecare" as the latest Democratic push for socialized medicine and higher taxes. Sen. John Barrasso, R-Wyo., called it "a complete Washington takeover of America's health care system."

Sanders dismissed those attacks. "You, the Republican Party, have no credibility on the issue of health care," he said Wednesday. "In the last few months, you, the Republican Party, have shown the American people what you stand for when you voted for legislation that would throw up to 32 million Americans off the health insurance they have."

NPR congressional reporter Scott Detrow contributed to this report.

Correction: September 14, 2017 12:00 am — A previous version of this article used the phrase "socialized medicine" to describe Bernie Sanders' plan. A more accurate descriptor is socialized insurance.

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