Through Medicare, the government health-insurance program created in 1965 to help older Americans afford their medical bills, the U.S. helps one in five of its citizens pay for doctor visits, blood tests, prescription drugs, stays in hospitals or nursing facilities, and hospice care. Why not offer those benefits to everybody? “Medicare for All” has emerged as a rallying cry among Democrats in the early stages of the 2020 U.S. presidential campaign, though it means different things to different people.

1. Who can get Medicare now?

About 85 percent of Medicare’s 59.7 million members are eligible because of their age — 65 or older. The rest are eligible because they have permanent disabilities. Beneficiaries are responsible for paying premiums, deductibles and other out-of-pocket costs, and most purchase some type of additional coverage to help with services that aren’t covered, such as long-term care, dental and vision treatment, and hearing aids.

2. What would Medicare for All mean?

That depends on who’s talking. Generally speaking, it suggests an end to the dominance of private health insurance in the U.S., in favor of either a government-run “single-payer” system, such as Canada’s, or a government-provided alternative to private insurance plans that Americans could buy into, an idea known as the “public option.” Less-drastic offshoots of the idea envision lowering the Medicare eligibility age to 50 — Medicare for more, rather than Medicare for All.

3. Which politicians support which proposals?

Senator Bernie Sanders, the Vermont independent who is again seeking the Democratic presidential nomination, continues to advocate for a fully government-run and government-financed system that would abolish most private insurance plans. Self-described progressive Democrats in the House of Representatives also favor a government-run single-payer system. That group includes Pramila Jayapal of Washington, who has offered specific legislation, and Alexandria Ocasio-Cortez of New York. Other Democrats vying against Sanders for the party’s 2020 presidential nomination are split (or fuzzy) over whether they would do away with most private insurance or, rather, seek more modest steps toward government-provided health care. House Speaker Nancy Pelosi’s focus on more modest steps toward insuring more Americans is an attempt to keep the party from fracturing over the issue.

4. Would Medicare for All change everybody’s health care?

It might, depending on the plan. The most expansive visions of Medicare for All, like those of Sanders and Jayapal, would establish universal benefits through a government-run program and outlaw most forms of private insurance, including employer-provided coverage. That might mean little if any out-of-pocket cost to patients, but also less choice for people who want to purchase specific types of benefits and for employers who use them to attract workers. Under a public-option plan, people satisfied with their insurance and medical care would have more flexibility to keep it.

5. How much would it cost?

The Congressional Budget Office, the provider of official cost estimates, hasn’t weighed in on any of the proposed plans. A study from the libertarian Mercatus Center said Sanders’ 2017 single-payer bill would raise federal spending by $32.6 trillion over 10 years; an earlier report by the nonpartisan Urban Institute reached a similar figure. (To pay for that, sponsors have floated ideas like raising taxes on the wealthy.) But the current system has costs as well. The U.S. spent $3.5 trillion on health care in 2017, or roughly $11,000 for each American, and is projected to spend about $47 trillion on health care between 2018 and 2027 (adding up what the government, employers and households pay). Today about 18 percent of gross domestic product goes to medical spending, a far greater share than most peer countries.

6. Would Medicare for All cut health-care costs?

That’s a matter of debate. Proponents say it would allow the government to limit costs by setting prices and eliminate the administrative burden of private health insurance. Critics argue that would remove the incentives private purchasers of health care have to steer their dollars toward more efficient, innovative suppliers.

7. Do Americans want Medicare for All?

That changes with how the question is phrased. In a January poll by the Henry J. Kaiser Family Foundation, 74 percent of those surveyed supported “creating a national government-administered health plan similar to Medicare open to anyone” if that meant people could choose to keep the coverage they already have. Support dropped to 56 percent if it meant “all Americans would get their insurance from a single government plan” and to 37 percent if it would “eliminate private health-insurance companies.”