The individual mandate began life as a Republican idea. Its earliest appearances in legislation were in the Republican alternatives to the Clinton health-care bill, where it was co-sponsored by such GOP stalwarts as Bob Dole, Orrin G. Hatch and Charles E. Grassley. Later on, it was the centerpiece of then-Gov. Mitt Romney's health-reform plan in Massachusetts, and then it was included in the Wyden-Bennett bill, which many Republicans signed on to.

If Republicans succeed in taking it off the table, they may sign the death warrant for private insurers in America: Eventually, rising cost pressures will force more aggressive reforms than even Obama has proposed, and if conservative judges have made the private market unfixable by removing the most effective way to deal with adverse selection problems, the only alternative will be the very constitutional, but decidedly non-conservative, single-payer path.