Today, Sen. Bernie Sanders unveiled his highly anticipated single-payer health care proposal, titled "Medicare for All." The bill is unlikely to pass in this Republican-controlled Congress, but currently 16 Democratic senators support the measure. Plus, there are at least two other concepts Democrats are pitching to expand coverage, and likely more are on the way.

Medicare for All The legislation pitched by Sanders would expand Medicare into a universal health care program guaranteeing insurance to all Americans, in what would create one of the nation's largest and most ambitious social welfare initiatives.

What it would do The Medicare for All bill would eliminate nearly all private health insurance in favor of a government-run system that ensures comprehensive coverage to every single individual through Medicare. In the first year, the eligibility age for Medicare would be lowered to 55, and those under 18 would immediately receive access to the program. Adults not currently eligible for Medicare would be phased in over four years.

in favor of a government-run system that ensures comprehensive coverage to every single individual through Medicare. In the first year, the eligibility age for Medicare would be lowered to 55, and those to the program. Adults not currently eligible for Medicare would be phased in over four years. The legislation proposes eliminating co-payments and granting all enrollees a generous and comprehensive set of benefits that includes coverage for everything from emergency surgery to mental health services to prescription drugs. The federal government would bear the cost of the program, which it would pay for through higher taxes.

and granting all enrollees a generous and comprehensive set of benefits that includes coverage for everything from emergency surgery to mental health services to prescription drugs. The of the program, which it would pay for through higher taxes. Sanders has not said exactly what Medicare for All will cost or settled on language raising the taxes necessary to support a universal health care system. During his presidential campaign, Sanders pegged the cost of an earlier version of his proposal at $10.38 trillion over a decade. However, other analyses estimated a much steeper price tag.

16 Democratic senators support it Baldwin (D-Wis.) Blumenthal (D-Conn.) Booker (D-N.J.) Franken (D-Minn.) Gillibrand (D-N.Y.) Harris (D-Calif.) Heinrich (D-N.M.) Hirono (D-Hawaii) Leahy (D-Vt.) Markey (D-Mass.) Merkley (D-Ore.) Schatz (D-Hawaii) Shaheen (D-N.H.) Udall (D-N.M.) Warren (D-Mass.) Whitehouse (D-R.I.)

Medicare Buy-In A group of Senate Democrats led by Debbie Stabenow is proposing legislation that would expand Medicare to allow individuals as young as 55 to buy into the government-run program. Connecticut Sen. Chris Murphy is also working on a Medicare buy-in plan of his own.

What it would do The proposal aims to provide Americans aged 55 to 64 with another, potentially lower-cost health insurance option, by allowing them to forgo private health coverage in favor of purchasing a Medicare plan.

by allowing them to forgo private health coverage in favor of purchasing a Medicare plan. Those who favor the bill also hope that expanding the Medicare program would help stabilize Obamacare's still-shaky individual insurance market , which has suffered from a disproportionate percentage of older and sicker enrollees. The bill would also make additional changes to the Obamacare markets in a bid to better prop them up.

, which has suffered from a disproportionate percentage of older and sicker enrollees. The bill would also make additional changes to the Obamacare markets in a bid to better prop them up. Democrats once considered lowering the Medicare eligibility age to 55 as part of Obamacare in 2009, but then-Sen. Joe Lieberman balked at the concept, endangering the broader law's path to passage and prompting negotiators to strip it out of the bill.

12 Democratic senators support it Blumenthal (D-Conn.) Booker (D-N.J.) Brown (D-Ohio) Cardin (D-Md.) Franken (D-Minn.) Gillibrand (D-N.Y.) Heinrich (D-N.M.) Leahy (D-Vt.) McCaskill (D-Mo.) Merkley (D-Ore.) Reed (D-R.I.) Whitehouse (D-R.I.)

Medicaid Buy-In Hawaii Sen. Brian Schatz is penning a proposal to allow states to give their residents the option to buy into the Medicaid program. The as-yet-unveiled bill would let states establish a kind of "public option" on their Obamacare exchanges by letting enrollees choose to purchase private health insurance or a Medicaid plan.