Health care was the most important issue for voters in last year’s midterm elections, and remains in that position as the nation begins to evaluate presidential candidates for the 2020 election.

Roughly 14% of Americans currently have no health insurance, according to a Gallup survey. 

There are a litany of proposals by candidates to change the health care system in the United States — ranging from expanding on the Affordable Care Act (ACA), informally known as Obamacare — to a single-payer system like Canada, creating a system of “Medicare for All,” and abolishing private health insurance in the United States.

A limited form of expansion to the ACA was actually proposed in its development by Congress in 2009, known as a “public option.” It would allow Americans to buy into a government-operated health insurance program, and would be a path towards providing “universal health care,” that is ensuring all Americans have some form of health insurance.

The public option is supported by presidential candidate Sen. Michael Bennet, D-Colo., who said during the presidential debates last month he supported its inclusion in the ACA, though it was removed from the final version of the bill.

Single-payer is a form of universal coverage provided for by government spending, financed by taxes. It exists throughout many European countries and Canada, among other states.

Sen. Bernie Sanders favors the abolition of private insurance and putting all Americans onto a government run program, which he calls Medicare for All. A recent Washington Post/ABC News poll found this position is supported by 43% and opposed by 49% of Americans. Sanders and Sen. Elizabeth Warren are the only candidates who support this policy.

President Donald Trump for his part has over the years supported various forms of health coverage, from universal health care to repealing and replacing the ACA with something “much less expensive and much better.”

Trump has not expanded his position beyond that, though in the wake of the failed attempt to repeal the ACA in 2017, Senate Majority Leader Mitch McConnell said efforts to repeal the legislation is no longer a “priority.”