“That estimate is not remotely realistic,” Blahous told the Washington Free Beacon. “Every credible analysis has found that the actual costs would be substantially higher, adding an amount of federal spending over the first decade of somewhere in the mid-30 trillions. It does not come close to acknowledging the costs of Medicare for All, let alone financing them.”

Warren reaches $20.5 trillion by starting with $33 trillion from the Urban Institute estimate, though the source of the $1 trillion disparity with Urban’s number is unclear. She then assumes $6 trillion in savings by redirecting funds that states spend on Medicare, an appropriation that could potentially face constitutional challenge.

To fill the remaining $7 trillion gap, Warren makes optimistic assumptions about potential cost-savings. In particular, she assumes that Medicare’s current low administrative costs will persist under an expanded regime. PolitiFact called the claim that Medicare has lower costs “half true,” noting that much of its costs are covered by the Social Security Administration.