Won’t single-payer health care require higher taxes? (Yes, obviously.) And won’t abolishing employer-sponsored insurance face opposition from some of the 160 million people happily on those plans now? (Almost certainly.)

At the debates, in post-debate spin rooms and on Sunday TV show interviews, the Democratic presidential candidates are asked these questions repeatedly as if they are “gotcha” questions. Then they duck and weave to avoid providing the honest but damning (affirmative) sound bite, instead offering some version of: I can convince voters they’d still come out ahead.

But in fact the real third rail of health-care reform — whether we’re talking about single-payer, a public option or anything else — is the question no one seems to be asking: Will you require doctors to make less money?

The United States spends a lot more on health care than other rich countries, about twice as much per capita. We have little to show for it, given our worse outcomes on key measures such as life expectancy and infant mortality.

Medicare-for-all proponents promise that their plans will cause us to resemble these other rich countries at last — not only in coverage, but in cost, too. How? By eliminating wasteful spending, which has lately come to mean taking on greedy private insurance companies and even greedier Big Pharma. […]