Senate Health, Education, Labor, and Pensions Committee member Sen. Elizabeth Warren (D-Mass.), third from left, speaks on Capitol Hill in January. Sen. Tim Kaine (D-Va.) is second from left. Sen. Michael Bennet (D-Colo.) is fourth from right. (Alex Brandon/AP)

A pair of swing-state Democrats are offering new legislation that would create Medicare-style options for non-elderly workers, with a heavy focus on rural areas that have few insurers offering coverage under the Affordable Care Act.

The proposal, from Sens. Michael F. Bennet (Colo.) and Tim Kaine (Va.), is politically significant because it tries to build on the existing law rather than the tear-it-all-down proposal of a national health-care system that is being offered by Sen. Bernie Sanders (I-Vt.).

Often called “single payer,” the Sanders proposal has gained steam among liberal activists who felt that last year’s failed presidential campaign by Hillary Clinton lacked a big progressive idea to galvanize the Democratic base. The single-payer plan, sometimes called “Medicare for All,” has already been embraced by many of the potential Democratic contenders for president in 2020, including prominent Senate Democrats such as Elizabeth Warren (Mass.), Cory Booker (N.J.) and Kamala D. Harris (Calif.).

However, overall, it has drawn only a third of the members of the Senate Democratic Caucus as co-sponsors, and even some supporters say the single-payer proposal is more of an “aspirational” goal. No one is certain how to finance an idea that would use Medicare as the basis for all health plans. Many Democrats worry that it would require huge tax increases that would kill the plan politically.

This shows the Democratic gap between those looking at the mood of national activists who will play a key role in selecting the party’s 2020 presidential nominee and those running in competitive congressional races next year that will determine the majorities in the House and Senate.

That’s where Bennet and Kaine come in, with what they call “Medicare-X,” legislation they are formally unveiling this week. It would allow anyone to buy into a publicly provided plan using the network of Medicare providers and physicians, at similar rates, with lower-income workers receiving tax credits for the plan. In its first years of operation, this new Medicare option would be available only in counties that have one or no providers offering insurance on the ACA’s private exchanges.

It would eventually phase in to all counties and would effectively serve as what Democrats called the “public option” in 2009 and 2010, when they debated and passed the health law under President Barack Obama. The public option, passed in the original draft by the House, could not clear a filibuster in the Senate and was dropped from the final bill. That came even though Democrats had 60 members in their caucus, enough to clear a filibuster, because several opposed a public option.

Bennet and Kaine are offering a proposal that they believe is both realistic and politically viable. The original targets for Medicare-X would be in rural areas that have been hardest hit by insurance providers fleeing ACA exchanges.

This would create, Bennet said in a statement given to The Washington Post, “a plan that begins to fix this problem by giving families and individuals a meaningful and affordable alternative.”

“Consumers can compare it with available private options and make the choice best for their health,” Kaine said.

Other Democrats have been trying to advance their own plans. Sen. Debbie Stabenow (D-Mich.) is proposing a bill that would allow people from ages 55 to 64 to buy into the actual Medicare program, while Sen. Chris Murphy (D-Conn.), sometimes mentioned as a 2020 contender, is preparing a buy-in proposal to Medicare that would be available to most of the public but would still compete with private insurers.

The public-insurance backup plan has gained currency in recent months as more insurers have withdrawn from the ACA’s marketplaces and left nearly half the nation’s counties with only one insurer in their marketplace for 2018.

These rural areas were the spots that broke most sharply against Clinton in the 2016 election, delivering larger shares of their votes to President Trump than to recent GOP nominees such as Mitt Romney and Sen. John McCain (R-Ariz.).

That could make this proposal a more palatable offering for the 10 Democrats up for reelection in states that Trump won last year, as well as many others in competitive states.

Bennet and Kaine are both examples of the latter. Obama and Clinton won Colorado and Virginia in the past three presidential contests, but by small margins. Both have won close, highly contested Senate races, and both have experience in national politics as well — Bennet chaired the Democratic Senatorial Campaign Committee in 2014, while Kaine was his party’s vice-presidential nominee last year.

Still, this proposal shows that Democrats have moved to the left ideologically on health care. Eight years ago, the public option failed because moderate Democrats backed away from it; now a similar proposal is being offered as the safe ground for those facing a tough reelection.

For many liberals, this proposal will not be sufficient, craving the universal promise that Sanders is offering. “Right now, if we want to move away from a dysfunctional, wasteful, bureaucratic system into a rational health-care system that guarantees coverage to everyone in a cost-effective way, the only way to do it is Medicare for All,” the 2016 runner-up to Clinton for the nomination told The Post last month.

Democratic leaders have tread carefully on the single-payer proposal, voicing support for its goal of universal coverage but also suggesting that the short-term objective is playing defense to protect the ACA from Republican efforts to repeal the law and to undermine the already shaky insurance exchanges.

“None of these things, whether it’s Bernie’s or others, can really prevail unless we protect the Affordable Care Act,” House Minority Leader Nancy Pelosi (D-Calif.) told reporters last month.

Bennet and Kaine are members of the Senate Health, Education, Labor and Pensions Committee and are supporting the ranking Democrat, Sen. Patty Murray (Wash.), in her negotiations with the chairman, Sen. Lamar Alexander (R-Tenn.), to forge a bipartisan deal to shore up the ACA. That might entail some changes to the ACA while also establishing better financial footing for private insurers to offer ACA plans in those underserved areas.

They do not expect Medicare-X to become the law of the land immediately, but Bennet and Kaine believe that this proposal could be the next step — once Democrats can win back some power in Washington — toward getting more people health coverage.

By maintaining the existing structure, rather than tearing it down, they believe that it could eventually become a potential bipartisan agreement that attracts Republican support to forge a law that is not under constant assault like the ACA.

“I want Virginians — and all Americans — to have more health-care choices,” Kaine said.

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