With Bernie Sanders’ Medicare for All bill introduced in the Senate, let’s get ready for a big debate about what it really is.

Most of it will take place on the Democratic presidential campaign trail, where all the major contenders say they are for it, but they all seem to mean something a little different.

And Republicans will be having their own debate, trying to figure out which monster under your bed is a scarier one – Medicare for All or a Green New Deal.

Before things heat up too much, it might be worth talking about what Sanders’ version of “Medicare for All” is by starting with what it is not.

For one thing, it’s not Medicare, at least not as we know it. Medicare is a half-century-old single-payer insurance program that covers hospitalization and doctor visits for people who are 65 and older, as well as younger people with disabilities.

Unlike Sanders’ bill, Medicare does not cover long-term care, and it does not cover prescription drugs, unless Medicare recipients buy a separate, optional policy. Medicare doesn’t cover dental care or glasses, but Sanders’ bill would.

People on Medicare usually buy private insurance to supplement their coverage unless they are low income enough to qualify for Medicaid, the federal and state health care partnership.

Sanders’ bill would wipe that out, giving everyone access to health care without private insurance, deductibles, co-pays or any other out-of-pocket costs.

The bill does not nail down a funding source, but Sanders says that shouldn’t be a problem. If you add up what’s spent through government programs, employer-provided private insurance, tax expenditures and out-of-pocket expenses, the United States already spends more on health care than any other country in the developed world – twice as much as Canada – and has worse results. Sanders figures we could actually spend less on a better system.

Which gets to what this version of “Medicare for All” really is. It’s a restructuring of the economy. By reallocating who pays for health care, Sanders would be narrowing the gap between rich and poor in a way we have not seen since the old New Deal in the 1930s.

Here’s how it might work: About half of Americans get their health insurance through work. Right now, a CEO making $300,000 a year and a janitor at the same company making $30,000 pay the same insurance premium.

If the employer tries to lower its costs by moving to a less generous plan – one with higher deductibles, or fewer covered benefits – the CEO and the janitor would have the same out-of-pocket responsibilities, even though one’s pocket is deeper than the other’s.

If both employees were covered by the new Medicare, and if it were funded by a progressive income tax, the CEO would be paying much more than the janitor. It would be easy to structure the tax so that most people would be paying less for their health care.

Since there are fewer rich people than not-rich ones, this should be a winning policy in a democracy.

Which leads to the other thing the Medicare for All is: A theory of democratic social change.

Sanders is not going to pass his bill by winning a debate in the Senate – there will not be a debate in the Senate unless Mitch McConnell wants one, and he doesn’t. He’s not going to lobby his buddies in the cloakroom or the gym. Sanders doesn’t seem to like other senators, and they don’t seem to like him.

And Sanders is not going to pass his bill by getting the hospitals, insurance companies and other interested parties to sit around the table and hammer out a bipartisan deal that everyone can live with. Sanders is not interested in a House bill that aims to fix some of the flaws in Obamacare. He’s not motivated to shave a few people off the list of the uninsured.

The only way Medicare for All has a chance (at least as envisioned by Sanders) is for its supporters to win elections, not just the presidency but many elections all across the country.

The last time any legislation approaching this magnitude became law was 1965, the year when Lyndon Johnson signed the Voting Rights Act, Medicaid and the original Medicare. The previous November he had been returned to office with 63 percent of the popular vote, along with 68 Democratic senators and a 145-representative Democratic advantage in the House.

If Medicare for All is the biggest social program ever conceived in our history, passing it would take that kind of landslide, moved by the biggest social movement we’ve ever seen.

To work in coalition with people who they don’t like very much and focus on economic justice, millions of people would have to put aside some issues that matter very much to them.

Over the next year, we’ll find out if that momentum exists. It’s what we’ll we be talking about when we talk about Medicare for All.