In June, as the fight over the repeal of the Affordable Care Act reached its climax, then-White House spokesperson Sean Spicer delivered a warning. “It’s not a question of Obamacare versus the AHCA,” he said, referring to the GOP alternative, the since-failed American Health Care Act. The question, Spicer said, was between repealing Obamacare and moving to single payer.

History may prove him right. When the battle over the ACA is finally over, the fight for what comes next will revolve around the bill introduced Wednesday by Sen. Bernie Sanders, aiming to create a universal Medicare program. It’s the most fleshed-out single-payer proposal ever introduced in Congress.

The campaign for the Vermont independent’s bill will start with the backing of at least 15 Democratic co-sponsors and 24 progressive and health care advocacy groups, numbers that will only grow in the coming days and weeks.

Read a chapter-by-chapter summary here or the executive summary here. See the funding options here.

The bill starts by sweetening the pot for seniors who may be wary about welcoming the rest of the country into their warm pool. It eliminates copays and deductions, except for name-brand drugs when generics are available, and adds dental, vision, and hearing aid coverage to Medicare — huge benefits that have long been a goal of public health advocates.

At the same time, people up to age 18 would be eligible for coverage in the first year. In year two, the eligibility age of 65 would be lowered to 45. The next year, it would drop again to 35. In year four, the age restrictions would be eliminated.

Importantly, Sanders’s bill repeals the Hyde Amendment, which restricts federal funding for abortions, as it relates to universal Medicare. That means that those covered would have full access to the entire suite of reproductive health care services, including abortions. His is the only single-payer legislation currently on the table that moves so strongly in the direction of reproductive freedom.

The history of the New Deal expansion shows that once benefits have been enacted, they are difficult to take away. Opponents of Social Security, Medicare, and Medicaid have been working to cut or privatize all three since the day each was enacted, but instead all have grown over time. (The major exception was Aid to Families with Dependent Children, better known as welfare, which was repealed in 1996.)

By phasing in coverage, Sanders makes universal Medicare harder to repeal and easier for the public to understand. Everyone gets that transitioning to Medicare when one turns 65 is a relatively painless process. Under Sanders’s plan, people would begin transitioning after the first year, at age 45 instead of 65. That’s not complicated.

The coverage for dental care will also be life-changing for millions of people who live in pain — some of whom, unable to afford proper dental care, are even forced to change their diets.

The new Medicare bill leaves the Veterans Administration in place and allows tribal health care systems to continue operations. It would allow doctors and providers to opt out of the system on an annual basis, meaning that a private system would exist alongside the public system.

The bill does not include an explicit funding mechanism. However, on Wednesday afternoon, Sanders’s office released a document laying out several options for financing the plan. The document is more or less a menu of various revenue mechanisms for the federal government to choose from. As the bill is debated in committee, Sanders said, senators can debate the various funding ideas.

The list includes, for instance, both household and employer-based premiums. The document proposes a 7.5 percent income-based premium on employers and a 4 percent income-based premium on households. Together, it estimates these two proposals would raise $7.4 trillion over ten years.

The document also notes that Medicare for All would eliminate various tax breaks that currently subsidize our current health financing system. This would raise $4.2 trillion over a decade.

Then there’s a large list of non-health care related taxes: everything from making the estate tax more progressive to taxing large financial institutions to establishing a wealth tax on the top 0.1 percent.

Sanders’s bill already has the backing of Democratic Sens. Elizabeth Warren of Massachusetts, Kamala Harris of California, Cory Booker of New Jersey, Al Franken of Minnesota, and Kirsten Gillibrand of New York, suggesting that the Democratic nominee for president — if they come from the ranks of politicians rather than Hollywood (Oprah, The Rock, etc.) — will more than likely back Sanders’s bill.

Presuming the Senate won’t move on the bill, its first real legislative debate would come if Democrats take the House of Representatives in 2018. Democratic members would face pressure in 2019 to study the bill in House committees and pass a version of it as something of a dry run. If Democrats follow a midterm wave by taking the White House in 2020, they’ll be positioned to move early on health care.

In 1993 and again in 2009, taking on health care at the front end of a Democratic administration turned out badly from an electoral perspective, but Democrats, if Wednesday is any indication, may believe the third time is a charm.