With the Republican health care bill apparently dead, congressional Democrats are brainstorming their own ideas for how to transform the health insurance system in case they take back power.

Sen. Bernie Sanders (I-VT) has captivated the base with a cry for Medicare-for-all, but other Senate Democrats worry his proposal — which envisions a vast overnight transformation of the health care system — will be difficult to pull off.

Now, Sen. Chris Murphy (D-CT), the latest entrant into the Democratic health care sweepstakes, says he is preparing a plan that would serve as a bridge between the current health care system and the single-payer system that has increasingly become the key demand of the party’s base.

Murphy’s idea: Allow every American, both individuals and companies, to purchase Medicare. Murphy’s hope is that if enough people purchase Medicare — and Murphy is confident they will en masse if they can — then the private health insurance would begin to shrink gradually. As a result, the government will swallow more and more of the private health insurance markets, setting up the trajectory for achieving a single-payer system.

“I have a feeling if everybody could buy into Medicare, people would choose to do so — and then you’d naturally transition to a single-payer system without a massive political fight,” Murphy said in an interview on Friday, citing opinion polls showing the popularity of the government program.

The plan is similar to a “public option” — an idea that was nixed from Obamacare by Murphy’s predecessor, Sen. Joe Lieberman (I-CT) — in that it also offers a government alternative to, rather than a replacement that would outlaw, private health insurance.

Murphy’s plan, first reported by Politico, follows alternative proposals from Sen. Brian Schatz (D-HI) and Sen. Sanders and comes as Democrats have moved with astonishing speed to embrace single-payer health insurance. But while Murphy casts his bill as an on-ramp to single-payer, it has important differences with Sanders’s bill — differences that make it simultaneously less ambitious, but also perhaps more feasible, than the Vermont senator’s proposal.

MurphyCare versus SchatzCare versus SandersCare, explained

To understand why Murphy is casting his proposal as a more feasible way to single-payer, you need to understand Sanders’s plan.

Sanders’s bill, set to be released on Wednesday, is expected to create a single government insurer to give Medicare free of charge to everyone in the country with virtually no copayments and no-deductibles. (Sanders’s Medicare-for-all bill is rumored to mirror a similar package from Rep. John Conyers (D-MI) in the House, explained at length here.) It would do so very quickly.

The clear upside of Sanders’s model is in ensuring the government provides universal coverage to all Americans free of cost; the downside is that it would require significant tax increases upfront, and force the 150 million Americans who currently get their insurance from their employer to join the government plan. Sanders advocates argue that the private health insurance should be eradicated

Sen. Schatz’s plan calls for every American to be able to buy into Medicaid. Medicaid’s benefits are more generous than Medicare, which may make it more appealing than Murphy’s plan; however, it is run by the states and thus leaves some experts worried that Republican governors could torpedo the effort to ensure the poor have adequate care.

Murphy’s plan tries to chart a third course. The Connecticut senator’s bill certainly would be less disruptive — engendering less opposition from private insurers — and it would also certainly represent a massive expansion of the government’s role in giving Americans insurance.

But one huge problem about Murphy’s plan is whether it would truly achieve universal coverage. Twenty-eight million Americans still don’t have insurance, including many who couldn’t or wouldn’t afford the deductibles and premiums of the insurers on the government exchanges. Medicare as it currently exists, rather than how Sanders would transform it, has significant cost-sharing — which means Murphy’s plan might price some people out.

“The question is if you need additional cost-sharing to make it affordable to people with middle incomes,” Murphy said, adding he was open to the idea. “You’d build it on top of the subsidies in the Affordable Care Act.

Murphy noted that he may wind up co-sponsoring Sanders’s bill, as did Schatz. “If I were building a health care system, from scratch, I’d start with a single-payer system,” he said.

Murphy has met with Sanders to discuss his alternative plan, according to a source with knowledge of that conversation. After all, Murphy said the two have the same goal.

“I think Medicare buy-in gets you to a single-payer system. This may be the fastest way to a single-payer system,” Murphy told me.