Democratic Primaries

The first problem for any single-payer push would be political support: Mr. Shumlin campaigned on a promise to build a single-payer system in Vermont, but the public never quite bought in. An April 2014 survey showed 40 percent support, 39 percent opposition and 21 percent undecided — a lukewarm result for such a major undertaking. That year, Mr. Shumlin barely won the popular vote against an anti-single-payer Republican. As John E. McDonough of Harvard wrote in a perceptive New England Journal of Medicine analysis of the plan’s collapse, “a clear public mandate” for Mr. Shumlin’s health care agenda “was nowhere in evidence.”

One reason the plan lacked strong support was lawmakers were cagey about how to pay for it. The 2011 proposal included no specific financing mechanism, because Mr. Shumlin’s team worried that might kill its chances.

Initial cost estimates were far too optimistic. A 2011 study led by William Hsiao of Harvard found that single-payer could reduce state health care spending by 8 percent to 12 percent immediately and more in later years, resulting in about $2 billion in savings over a decade. But by the time Mr. Shumlin ditched the plan, internal government estimates showed a five-year savings of just 1.6 percent.....

The Vermont plan was done in by high taxes, distrust of government and lack of political support. Any effort by a Sanders administration to enact a single-payer system at a national level would probably be doomed by similar problems.....

But if it couldn’t work in Vermont, with a determined governor, an accommodating legislature and progressive voters, Mr. Sanders will have a tough time explaining why it will somehow succeed on a vastly larger scale. Vermont represents a practical failure on friendly turf, and that is what makes it such a powerful counter to Mr. Sanders’s proposal.

“If Vermont can pass a strong single-payer system and show it works well, it will not only be enormously important to this state, it will be a model,” Mr. Sanders said in 2013.

As it turns out, it was a model. But instead of showing us how it would work, it showed us why it would fail.