At the debate, as throughout the campaign, Warren refused to provide any specifics about how she would fund a single-payer plan. Instead, whether questioned by moderators or challenged by other candidates, she recycled variants on the same talking points she has used in venues from campaign town halls to a recent appearance on The Late Show With Stephen Colbert. Rather than explaining what revenue she would raise to fund the plan, Warren insisted that under single payer, middle-income families would save more money with the elimination of health-care premiums, co-pays, and deductibles, regardless of any taxes imposed. “Costs will go up for the wealthy and for big corporations, and for hard-working middle-class families, costs will go down,” she said at the debate.

Read: The risk of Elizabeth Warren’s dodging

That calculation itself is disputed. And it begs the question: Even if families would eventually save under a single-payer system, a President Warren would still need to identify a politically plausible funding plan to pass such a program through Congress. By all indications, that looms as an extremely daunting project.

The new Urban Institute study helps define the magnitude of the task Warren (or Sanders) would face. The think tank modeled the costs of eight possible plans to expand health-care coverage that generally track ideas from the Democratic presidential candidates. By far, the most expensive was its version of the single-payer plan that Sanders introduced in the Senate and that Warren later endorsed: a blueprint that would eliminate private health insurance, require no co-pays or premiums from individuals, and provide everyone in the United States (including undocumented immigrants) an expansive benefits package including dental, vision, and home health care.

The 10-year cost of $34 trillion that the study forecasts nearly matches the CBO’s estimate of how much money the federal government will spend over that period not only on all entitlement programs, but also on all federal income support, such as the Supplemental Nutrition Assistance Program. Former Vice President Joe Biden said incorrectly at the debate that the single-payer plan would cost more annually than the total existing federal budget—it would cost less. (The CBO says Washington will spend about $4.6 trillion in 2020.) But over the next decade, the plan on its own would represent a nearly 60 percent increase in total expected federal spending, from national defense to interest on the national debt, according to CBO projections.

The Urban Institute estimates that a single-payer plan would require $32 trillion in new tax revenue over the coming decade. That’s slightly less revenue than its projected cost, because it would generate some offsetting savings by eliminating certain tax benefits the government now provides, such as the exclusion for employer-provided health care.