When President Barack Obama and Democrats in Congress began pushing for what became the Affordable Care Act, they felt compelled to reassure the American people that they could keep what they had for private health insurance.

There's a reason they made such a promise for the now 150 million people in employer-based plans. When it comes to healthcare finance reform, most Americans are leery of scrapping their existing coverage for a government-run plan, the single-payer proposal being offered by Sen. Bernie Sanders of Vermont.

Yes, a majority in the latest Kaiser Family Foundation poll backed “Medicare for all” (34% strongly favor; 24% somewhat favor). But as liberal writers Ezra Klein of Vox and Henry Aaron of the Brookings Institution have noted, that support would wither once people become aware of the taxes involved or its implications for patients and the delivery system once the government began setting provider payment policy (code word: rationing).

Americans have also shown little enthusiasm for the radical nostrums offered by the many conservative politicians competing for the Republican nomination. Almost all want to turn federal support for Medicaid into block grants to the states and fully privatize Medicare. They ignore the fact that 75% of Medicare beneficiaries and 65% of Medicaid beneficiaries say the programs are working well, according to another Kaiser poll.

Moreover, not one of the Republicans running for president has offered a solution for the tens of millions of Americans still without coverage. None backing repeal of the ACA has said how they would handle the 20 million who gained coverage under the law.

So as we enter a 2016 election cycle taking place in the wake of the biggest health insurance expansion since the advent of Medicare and Medicaid in the mid-1960s, the best that can be said of the changes being offered by presidential aspirants is that they are impractical, unimaginative and unpopular.

This is not an endorsement, simply an observation: There are only three candidates—Ohio Gov. John Kasich, former Secretary of State Hillary Clinton and former Maryland Gov. Martin O'Malley—who embrace the model created by center-right conservatives, first applied by former Massachusetts Gov. Mitt Romney and accepted by Obama and the mainstream of the Democratic Party. It relies on private insurance companies selling health plans through state-based exchanges, with government subsidies for those too poor to afford the plans. Who finds themselves in this sorry condition? Those who are unemployed or whose employers don't provide coverage.

In case anyone has forgotten, it is the Swiss cheese-like nature of employer-based coverage that created the uninsured problem in the first place.

And that's really where a political discussion about the next steps in healthcare reform ought to start. The tax-advantaged, employer-based health insurance system, a legacy of World War II wage-and-price controls, is unfair in every way.

Some employers don't bother offering coverage. From an economist's perspective, they are free riders on a system paid for by others.

For those that do provide coverage, excluding those benefits from taxable wages means those in the highest tax brackets get the biggest tax breaks.

It is unfair to employers in other ways beyond the free-rider problem. Employer-based coverage breaks the insured population into risk pools that do not reflect the larger society. General Motors pays significantly more for health benefits for its mostly older workforce of 214,000 than does Google for its 53,000 mostly younger employees.

We need a health insurance system for the 21st century that allows people to maintain coverage as they move between jobs or engage in the so-called “gig” economy—the fate of most workers in today's society. It should eliminate arbitrary risk pools, provide for consumer choice, rely on fairer taxes and give subsidies where they are needed.

We can get there from here. But the change needs to be gradual. And it can happen only if our politicians embrace the potential in the state-based exchanges begun under Obamacare. In next week's editorial, I will sketch out what such a system might look like.