If there's one issue that defines Sen. Bernie Sanders, it's probably his unflinching support for a government-run health care system that's financed through federal taxes. That idea of "Medicare for All" has become a defining issue in the larger Democratic presidential race — and some other candidates are proposing modifications to Sanders' plan.
Under Sanders' Medicare for All plan, there would be a four-year transition period before everyone would be enrolled in a greatly expanded Medicare program that would offer more generous benefits than the current system.
Sanders says there would be no deductibles, no co-payments or out-of-pocket expenses. Virtually all private health insurance plans would be eliminated and individual premiums would be replaced by new taxes.
Sanders insists that the overall cost will be substantially lower for most people thanks to reductions in administrative costs and drug expenses.
More from NPR — "Sen. Bernie Sanders Defends His 'Medicare For All' Plan" [July 17]
Jeff Weaver, a senior adviser on the Sanders campaign, said health care is one of the most important issues in the Democratic race.
"Clearly very positive terrain for us. ... It also shows a clear differentiation among the candidates in terms of who is willing to take on the big insurance companies and the big pharmaceutical companies to benefit working Americans," Weaver said.
But Ted Kohn, dean of the College of Liberal Arts at Norwich University, said he thinks Sanders is taking a major risk by supporting a plan that eliminates private insurance.
"Once you start drilling down on how are you going to pay for it, on are you going to be able to keep your private health care, then suddenly support for Medicare for All — even among the Democratic base — seems a lot more tenuous,” Kohn said.
And then there's how the plan is being framed to voters. Linda Fowler, a professor emerita of government at Dartmouth College, said she thinks the Medicare For All plan is hard for voters to understand, making it easy for opponents to misrepresent how it works.
"This kind of thing is easily gamed ... by Sanders' opponents because of the widespread mistrust of the federal government," Fowler said, "and even though he can say that costs are much lower for Medicare than with private insurance, all of which is true, but it's a complicated argument to make."
In the past few weeks, three Democratic presidential candidates who are sponsors of Sanders' plan — California Sen. Kamala Harris, New Jersey Sen. Cory Booker, and New York Sen. Kirsten Gillibrand (who just dropped out of the race)— have modified their approach because they're concerned it represents too much change too fast.
They now want participation in Medicare to be optional and private health insurance companies would continue to operate under their plans. Their approach is known as "Medicare For All Who Want It."
But that's a position that Weaver says Sanders will never support.
"It's a much safer political path so, you know, between the combination of not wanting to alienate donors and then making sure that you ... promise the least bold change because, you know, a certain group of consultants view that as the smart way to go, I think those are two big drivers of this,” Weaver said.
There could be another challenge for Sanders on this issue: Former Vermont Gov. Peter Shumlin abandoned efforts for a single-payer plan because of the large tax burden that was needed to support it. Fowler thinks this example will become a key issue in the Democratic race.
"It will be very easy to say 'Vermont adopted a plan that's not as generous as the one you're advocating and weren't able to implement because of the costs,'" said Fowler. “If that doesn't come up in the September debate, I'd be surprised."
The third Democratic presidential debate is scheduled to take place in about two weeks, and health care is expected to be a major topic.
Update 6:52 p.m. This post was updated to reflect Gillibrand's decision to drop out of the presidential race.