(Bloomberg View) — The Republicans' failure to repeal Obamacare has created a political opening. The American public, threatened with the withdrawal of health insurance from millions of people, has largely come to embrace the idea of universal coverage. At such a moment, Democrats are right to advance ideas for building on the gains accomplished by the Affordable Care Act.

Unfortunately, many of them are supporting Senator Bernie Sanders in his drive for a single-payer system. Universal coverage does not require single-payer — and pressing for that particular form of universal coverage is unwise both on the merits and as a matter of political strategy.

The legislation that Sanders introduced Wednesday — endorsed already by more than a dozen Democrats, several of whom might run for president — is needlessly radical. Supporters seem captivated by its apparent simplicity: Sweep away the current fragmented, wasteful system and have the federal government pay for all health care. In fact, implementing such an enormous, wrenching change might not save money and would be anything but simple.