WASHINGTON — Bernie Sanders for years has waged a lonely Senate battle for legislation to create a single-payer, government-run health care system. Now, the Vermont independent, who has never had a co-sponsor for his bill, has quite a bit of company.

Sixteen Democrats — including potential 2020 presidential candidates — have lined up behind his “Medicare-for-All” bill, which would eliminate the role of private insurers in basic health care coverage. More than 500,000 people across the country have signed a petition as “citizen co-sponsors” of his bill, which he introduced today in a packed Senate hearing room.

In the House, a record majority of Democrats — 117 — have signed onto similar legislation by Rep. John Conyers of Michigan.

“There is no doubt about it, momentum is on our side,” wrote Sanders, who pushed the idea as a 2016 presidential candidate, in an email to his supporters Wednesday.

But momentum is hardly passage, and the bill faces an uphill climb in a Republican-controlled Congress that is still trying to unravel Democrats' last overhaul of the American health care system: Obamacare.

Here’s what a Medicare-for-all bill could mean for you:

What would be covered?

The Sanders bill would allow for comprehensive coverage, from hospital to dental services, and it would include abortion coverage. Patients would choose doctors, hospitals and other health care providers they want, and they would pay no deductibles or premiums.

Benefits would remain the same for veterans and Native Americans, who receive medical care through the Indian Health Service.

Sanders' bill would also take preliminary steps to expand Medicare during a four-year transition period before making Medicare coverage universal. Other Democrats have suggested less drastic changes, such as providing an option for Americans to buy in to Medicare or extending Medicare only to people over 55.

Republicans say single-payer health care countries such as Canada and the United Kingdom face poor quality of care and long wait times to see a doctor.

“Some patients will never get the care they need,” Sen. John Barrasso, R-Wyo., wrote about the idea in a Fox News opinion piece. "When Washington pays all the bills, it will soon decide to exert tighter control over everybody’s care."

Sanders counters that America already rations health care, with thousands dying because they can’t afford it. Meanwhile, he says Americans' life expectancy is lower than most other industrialized countries and infant mortality rates are much higher.

"We spend almost twice as much per capita on health care as any other nation on Earth and yet we have 28 million people without any health insurance and even more who are under insured," Sanders said.

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How much would it cost me?

Under Sanders’ bill, Americans would have one insurance plan, administered by the federal government. Gone would be co-pays, deductibles and premiums paid to private insurers along with insurance that’s tied to employment.

Sanders provides no estimate of what “Medicare for all” would cost the federal government, and therefore cost in taxes on the average person, but he says it would take a much smaller percentage of most Americans’ income.

"While, depending on your income, your taxes may go up to pay for this publicly funded program, that expense will be more than offset by the money you are saving by the elimination of private insurance costs," Sanders said.

He also expects the price of drugs to drop for the federal government and individuals because the bill would lift the current ban on the federal government negotiating prices with drug companies.

But won’t it cost a fortune in taxpayer money?

Yes, if estimates of Sander’s campaign proposal are any gauge.

Republicans point to an Urban Institute study indicating that proposal would increase federal expenditures by $32 trillion over 10 years. Another study by the Committee for a Responsible Federal Budget says the campaign proposal would cost $25 trillion and add $16 trillion to the debt (including interest) without additional offsets, putting the national at 148% of GDP in 2027.

Sanders' staff says the actual bill will cost less than the campaign plan, but the bill hasn’t yet been scored by the non-partisan Congressional Budget Office.

Sanders proposed options to finance the bill that he says together would raise about $16 trillion over 10 years. Among them are income-based premiums paid by employers or households, a more progressive personal income tax, a "wealth tax," a one-time tax on corporate profits held offshore, and a fee on large financial institutions.

Could it pass Congress?

Nope, not in a Republican-controlled Congress. In fact, four Democrats and one independent joined Republicans in opposing a single-payer bill when Republicans forced a vote in July. Other Democrats voted “present” at the request of Sanders, who called the GOP move a “sham.”

But progressive Democrats expect candidates for president and other offices to rally behind ideas for Medicare expansion in the next elections. Along with Sanders, Senate co-sponsors include others who are regularly mentioned as potential presidential candidates: Elizabeth Warren of Massachusetts, Kamala Harris of California, Cory Booker of New Jersey and Kirsten Gillibrand of New York.

Adam Green, co-founder of the Progressive Change Campaign Committee, said activists will push the Democratic Party to embrace the idea of Medicare-for-all in coming years, and it will be a political winner because Medicare is so popular.

“Voters will get the message that the Democratic Party stands for a big idea of giving every American access to the super popular Medicare program,” he said.

Several Democratic leaders have co-sponsored the House bill, but Minority Leader Nancy Pelosi of California isn’t among them, even though she has long supported the single-payer approach to health care.

“Right now, I’m protecting the Affordable Care Act,” she told reporters.

Republicans are still trying to overturn that law, and they were forced back to the drawing board in July after the Senate narrowly defeated a limited repeal of what is better known as Obamacare. On Wednesday, President Trump endorsed yet another GOP plan that would replace parts of 2010 law, and the Senate Health Education, Labor and Pensions Committee has been holding hearings this month on bipartisan options for propping up the current law.

Is there public support?

Support for single-payer health coverage has been growing, with 33% of those surveyed favoring this approach to health insurance compared with 21% in 2014, a Pew Research Center poll found in June.

The share of Democrats (52%) supporting a single national program to provide health insurance is up 19 points since 2014. But nearly two-thirds of liberal Democrats (64%) support single-payer health insurance while only 42% of conservative and moderate Democrats favor that approach.

The idea received greater support – 60% — in an April poll by The Economist/YouGov that asked whether respondents favored “expanding Medicare to provide health insurance to every American.”

Those who said they favored the idea strongly or somewhat included 75% of Democrats, 58% of independents and 46% of Republicans.