Matt Rourke / AP

Bernie Sanders faced more pointed attacks last night over his potential vulnerabilities than he ever has at a debate. But the blustery and disorderly session once again failed to fully explore what could be the Vermont senator’s greatest general-election weakness: the massive size and scope of his spending and tax proposals, which, depending on the estimate, would cost $50 trillion to $60 trillion over the next 10 years. That would roughly double the size of the federal government, an unprecedented increase outside of wartime.

More so than in any previous session, Sanders at times seemed rattled and tentative as his rivals subjected him to a crossfire of criticism—over his record on gun control; my colleague Edward-Isaac Dovere’s report that he seriously considered a primary challenge to Barack Obama in 2012; his praise for aspects of Fidel Castro’s record in Cuba; and his success, or lack thereof, at getting things done in Washington. The evening showed “the first sign of uneasiness” for Sanders on a debate stage in this election cycle, says Lily Adams, the former communications director for Kamala Harris’s presidential campaign. “For the first time, we saw moments where he was not 100 percent sure of what his rebuttal was going to be.”

But Sanders benefited from the chaotic nature of the debate, which prevented his rivals from sustaining any individual line of attack against him for very long. And when he wasn’t on the defensive, he confidently delivered his populist promise to deliver an economy that works better for working families.

Still, the debate’s most lasting effect may be the seeds it laid down for a deeper discussion to come about the cumulative cost of Sanders’s agenda, an issue that’s received remarkably little attention until recently.

Sanders arrived at the debate facing rising criticism over his refusal to explain how much his proposals would cost and what taxes he would raise to pay for them. On Sunday, on 60 Minutes, he brushed aside questions from Anderson Cooper about the full price tag, insisting, “Well, I can’t—you know, I can’t rattle off to you every nickel and every dime.” During a CNN town hall in Charleston on Monday, Sanders tried to preempt further questions by handing the moderator, Chris Cuomo, a document that he said cataloged all his spending plans, including the taxes—almost entirely on the wealthy and business community—that he’s proposing to pay for them. Yet the document inadvertently may have demonstrated only how difficult it will be for Sanders to produce a politically acceptable plan to fund his spending.

“You would need even more revenue than he is proposing to fully offset those costs,” says Jared Bernstein, an economist and senior fellow at the liberal Center on Budget and Policy Priorities who is generally sympathetic to Sanders’s agenda. “It is not realistic to believe you can get all those revenues from the top 1, 5, or 10 percent [of households]. You would have to go down further than that. The rest of it has to come from a broader base of taxpayers or it has to go on the deficit.”

The document Sanders released identifies seven major spending proposals from his campaign:

  • $16.3 trillion for a Green New Deal, to accelerate the transition to a carbon-free economy;
  • $1.5 trillion to provide universal prekindergarten and child care;
  • $2.2 trillion to provide tuition-free public college and university, and to forgive all student debt;
  • $2.5 trillion to build affordable housing and reduce homelessness;
  • $81 billion to write off all medical debt;
  • a proposal to increase Social Security benefits (which Sanders did not provide a cost estimate for, but which other analysts have put at costing as much as $1.4 trillion); and
  • his Medicare for All plan, whose 10-year cost estimate in new federal spending ranges from just less than $31 billion (from the nonpartisan Committee for a Responsible Federal Budget) to $34 trillion (from the center-left Urban Institute).

Sanders has also embraced other expensive spending plans that he did not list, notably: increased funding for K–12 education, which has been estimated to cost $800 billion to $1 trillion; a federally funded paid-medical-and-family-leave program for workers, which the Congressional Budget Office recently scored at about $500 billion over a decade; a $1 trillion infrastructure initiative; and a federal guaranteed-jobs program whose cost estimates vary widely but that could run into the trillions.

These numbers are estimates—subject to inevitable uncertainty and imprecision. But their general direction is clear. I recently calculated that their cumulative price tag would reach about $60 trillion over 10 years. The Progressive Policy Institute, a centrist Democratic think tank, put the 10-year cost at about $55 trillion. It assumed a slightly lower cost for Medicare for All and projected that Sanders could fulfill his federal jobs guarantee and infrastructure promises through his Green New Deal and universal-child-care programs, without any additional expenditure.

At either number, the Sanders agenda would roughly double the $52 trillion that the Congressional Budget Office projects the federal government will spend over the next decade on all existing programs, from defense to Social Security. Even at a lower, $50 trillion estimate, the Sanders plan would increase federal spending as a share of the economy by about 20 percentage points, according to calculations that Larry Summers, the former Treasury secretary under Bill Clinton and former chief economist at the World Bank, shared with me earlier this winter. Franklin D. Roosevelt’s New Deal, the largest 20th-century peacetime spending program, increased federal expenditures as a share of GDP by eight percentage points, according to Summers’s calculations.

Until now, Sanders has responded to questions about his agenda’s cost by focusing only on his vision for Medicare for All, insisting that most Americans would spend less than they do now—even if their taxes are increased—because the plan would eliminate their insurance premiums, co-payments, and deductibles. The document that Sanders handed Cuomo on Monday represents his most complete attempt to explain how he would cover the bill for his entire agenda. But critics quickly noted that it falls well short of the full price tag for his plans—and almost certainly overstates the funds they would generate.

Sanders identified just over $30 trillion in new taxes that he’d raise over the next decade, almost entirely from businesses and the affluent. He identified roughly another $12 trillion in other revenue and savings, including a $1.2 trillion cut in defense spending and $6.4 trillion he said the government would earn under his Green New Deal plan by selling electricity from new renewable-power facilities.

If Sanders’s tax plans were to raise as much money as he claims, they would increase federal taxes as a share of GDP by as much as 11 percentage points. “I think it is fair to say that the tax increase—assuming it is as big as Senator Sanders projects—is about as large as the [13-point] tax increases enacted to finance World War II,” as measured as a share of GDP, says Leonard Burman, a former senior Treasury Department tax official under Clinton and an institute fellow at the Tax Policy Center, which is operated by the Urban Institute and the Brookings Institution. “It is more than five times as large as any tax increase enacted since. And even if it falls short of the campaign’s projections, it would be the largest peacetime tax increase in American history.”

Burman, like other analysts, believes that Sanders is overestimating the revenue that several of his tax proposals would produce. A new analysis from Ben Ritz, the director of the Progressive Policy Institute’s Center for Funding America’s Future, concluded that Sanders’s proposals would generate about $29 trillion in taxes, other revenue, and savings over 10 years, an unprecedented peacetime increase, but nonetheless about $25 trillion or more short of his plan’s total bill. (For comparison, that shortfall is about as much as the Congressional Budget Office projects the federal government will collect from the entire personal-income tax over that period.) Because he’s already exhausted almost every conceivable proposal to raise taxes on the rich, Ritz says, Sanders has only two options to cover the difference: “He’s either going to have to borrow the money or take it from the middle class.” In his stump speech and in debates, Sanders never acknowledges those possibilities.

Bernstein says that judging Sanders’s plan against such precise yardsticks is a mistake. The sheer size of his proposals, which dwarf the spending plans of any modern Democratic presidential nominee, should signal that they are more “aspirational than realistic,” Bernstein says. There is very little chance, he notes, that even if elected, Sanders could implement such a huge increase in government spending. Instead, he says, Sanders is offering a vision of a society where the government plays a much larger role in delivering social services, from education to health care—one that looks more like a Scandinavian country than America at any point in its earlier history.

“That’s just a very different economy than we’ve ever had or contemplated here,” says Bernstein, who served as the chief economist in Joe Biden’s vice-presidential office. “That’s not a value judgment. If we choose to have an economy with far more government in it, that model exists … People like Bernie and Elizabeth Warren are actually very explicit about this. They think the current model is broken and they are espousing a different one.”

To Bernstein, Sanders’s agenda is valuable less as a specific blueprint for governing than as a signpost for the direction he’d try to take American society in the years ahead. But other Democrats are terrified that voters might react less philosophically if presented with such an expansive—and expensive—program this fall.

“I'll tell you exactly what it adds up to,” former South Bend, Indiana, Mayor Pete Buttigieg said last night. “It adds to four more years of Donald Trump, Kevin McCarthy as speaker of the House, and the inability to get the Senate into Democratic hands.”

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