Most Democratic presidential candidates are supporting some version of Medicare for All, a radical proposal to put Washington in complete control of the health-care system. Joe Biden, however, promises to “protect and build on the Affordable Care Act,” the last Washington health-care experiment, which is better known as ObamaCare.

Yet ObamaCare largely failed in its primary goal—to create a better market for individual health insurance. The ObamaCare exchanges are performing much worse than expected when they were launched in 2014. And this has nothing to do with the Trump administration. Rather, the law failed because of its perverse construction.