Associated Press

Sen. Bernie Sanders is facing increasing pressure to explain how he'd pay for his signature plan, Medicare for All.

He has previously declined to provide estimates, but his stance is starting to open him up to attacks from rivals like Biden and Buttigieg.

The Urban Institute estimated last year that a comprehensive healthcare system on the scale Sanders is seeking would cost $34 trillion over a decade.

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Sen. Bernie Sanders is surging in Iowa ahead of its February 3 caucus, but the increased prominence is coming with escalating scrutiny from Democratic presidential rivals over a key part of his progressive agenda: Medicare for All.

The pressure comes after a CBS News interview that aired Friday, where Sanders doubled down on his refusal to give a price tag for the creation of a single-payer healthcare system that would insure every person in the US.

Asked directly about its cost, Sanders declined to provide an estimate, saying, "Nobody knows. This is impossible to predict."

However, he held that a federal health insurance system under Medicare for All would be cheaper than maintaining the status quo.

Back in October, Sanders said in a CNBC interview he didn't believe he needed to outline the specifics of his plan for universal healthcare anytime soon, arguing that middle-class Americans would save money in the long run even if they faced a tax increase.

The Urban Institute estimated last year that a comprehensive healthcare system with no premiums, deductibles, or out-of-pocket costs on the scale Sanders seeks would cost $34 trillion over a decade. Several independent analyses of Medicare for All proposals, though, suggest it can lead to considerable savings through federal negotiation of lower prices and less administrative spending.

But the Vermont senator's refusal to lay out additional details on how he'd pay for the plan is opening him up to blowback, notably from moderate rivals former Vice President Joe Biden and former South Bend Mayor Pete Buttigieg, according to The Hill.

Carlos Barria/Reuters

Biden recently went on the offensive against Sanders, his ascendant rival in Iowa, without calling him out by name. He warned that Sanders would be undercut by his own lack of financing details trying to pass Medicare for All through Congress.

"Well, that's not a likely way to pass something through the Senate, saying, 'I don't know how much it's going to cost,'" Biden said, without naming Sanders directly.

Buttigieg also piled on in a campaign appearance, saying he thought Sanders wasn't being straightforward with the public.

"Call me simplistic, but I think when you put forward a plan, you ought to put forward how to pay for it, too," the former mayor said.

The criticism echoes the attacks Sen. Elizabeth Warren faced late last year, as she surged through much of the summer wielding an array of sweeping plans to fundamentally restructure the American economy.

Warren was initially a vocal supporter for Medicare for All, and for several weeks she faced substantial criticism after declining to say whether it would lead to a tax increase for the middle class.

Then the Massachussetts senator put forward a two-step $20.5 trillion plan that proposed a public option first that would eventually lead to single-payer healthcare without raising taxes on most Americans.

The Warren campaign did not respond to a request for comment. But experts have said that her quest to become the Democratic nominee and progressive standard-bearer was damaged as a result.

"When you look at the polling she definitely paid a price for it," said Mary Anne Marsh, a Boston-based Democratic political strategist, adding that she believes Sanders hasn't been held to the same standard, with gender being a factor.

"It's great to talk about these things, but if you don't talk about it, voters should know and that's part of the measurement every voter should have when they head to the polls," Marsh said.

How Sanders could pay for Medicare for All

Sanders has unveiled a series of possible options to cover the full cost of Medicare for All. Among them:

A 4% income-based premium that employees pay, exempting the first $29,000 of income for a family of four.

A 7.5% income-based premium that employers pay, exempting the first $2.5 million of payroll.

A more progressive federal income tax system with a 70% marginal tax rate on people earning more than $10 million per year.

An end to health tax expenditures.

Larry Levitt, the executive vice president of health policy at the Kaiser Family Foundation, said that though the Sanders Medicare for All bill is detailed, it leaves two significant issues unanswered: how much doctors and hospitals would be paid and which taxes go up to insure every person in the US and replace premiums and deductibles.

"One of the most important things I've learned in health care is that getting specific about the difficult trade-offs rarely makes a health reform plan more popular," Levitt said in a tweet.

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