In September, two weeks before the Affordable Care Act was due to launch, President Obama declared that "there's no serious evidence that the law . . . is holding back economic growth." As for repealing ObamaCare, he added, "That's not an agenda for economic growth. You're not going to meet an economist who says that that's a number-one priority in terms of boosting growth and jobs in this country—at least not a serious economist."

In a way, Mr. Obama had a point: "Never met him," says economist...