(Bloomberg View) — The Republicans' failure torepeal Obamacare has created a political opening. The Americanpublic, threatened with the withdrawal of health insurance frommillions of people, has largely come to embrace the idea ofuniversal coverage. At such a moment, Democrats are right toadvance ideas for building on the gains accomplished by theAffordable Care Act.

Unfortunately, many of them are supporting Senator BernieSanders in his drive for a single-payer system. Universalcoverage does not require single-payer — and pressing forthat particular form of universal coverage is unwise both on themerits and as a matter of political strategy.

The legislation that Sanders introducedWednesday — endorsed already by more than a dozenDemocrats, several of whom might run for president — isneedlessly radical. Supporters seem captivated by its apparentsimplicity: Sweep away the current fragmented, wasteful system andhave the federal government pay for all health care. In fact,implementing such an enormous, wrenching change might not savemoney and would be anything but simple.