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.

Fifteen Democrats — including potential 2020 presidential candidates — have lined up behind his “Medicare-for-All” bill that 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 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.

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.

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

Other Democratic proposals being discussed would provide for a Medicare option for all or a Medicare option for those 55 and older. Sanders, as well, would take preliminary steps to expand Medicare during a four-year transition period before making Medicare coverage universal.

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 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 America already rations health care, with thousands dying because they can’t afford it.

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 average person, but he says it would take a much smaller percentage of most Americans’ income.

He expects the price of drugs to drop for the federal government and individuals because the bill would lift the federal government’s current ban on 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.

A Sanders aide says the bill will cost less than the campaign plan.

The bill hasn’t yet been scored by the non-partisan Congressional Budget Office.

Could it pass Congress?

Nope, not in a Republican-controlled Congress. In fact, four Democrats and one independent joined Republicans in opposing the House proposal 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 they back for president and down the ballot 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 the 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 House 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.

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 to 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.