Rich Lowry‘s latest column at National Review Online sets out a disappointing progress report for the Affordable Care Act.

For years, Obamacare supporters have been telling critics of the law to shut up and fall in line. Now, they are urging them to come to its rescue.

A key part of President Barack Obama’s domestic legacy is sputtering so badly that even the law’s boosters are admitting that the federal government needs to do more to prop it up. The Obamacare exchanges were supposed to enhance choices and hold down costs — and are doing neither. Abandoned by more and more insurers, the exchanges — once billed as robust “marketplaces” — are becoming pitiful shadows of themselves.

In most or all of states like Alaska, Alabama, Arizona, Florida, Missouri, Oklahoma, North Carolina, and Tennessee, probably only one insurer will offer insurance through the exchanges next year, reports the Wall Street Journal. One large county in Arizona may have no exchange insurer at all. An analysis by the Kaiser Family Foundation finds that 31 percent of counties in the U.S. will have one insurer, and another 31 percent will have just two.

It isn’t Republicans who are hobbling the law. It isn’t the greedy insurance companies, which were over-optimistic about the exchanges at the outset and are now paying the price. It is fundamental economic forces that the law’s architects blithely ignored. But economic incentives will not be mocked.