In America's courtrooms, ObamaCare is on trial. A majority of states have filed lawsuits arguing that its mandate requiring individuals to purchase health insurance is unconstitutional. But in Vermont, ObamaCare is about to get a trial of a different sort—a clinical one.

This coming Thursday, Gov. Peter Shumlin will sign a bill doing what President Obama and his allies have hoped to do all along: sell a public insurance option alongside competing private insurance as a first step toward a single-payer, government-run system....