Most of the debate about the Affordable Care Act has centered on how it affects health care. It’s time to pay attention to how ObamaCare has damaged federal finances. Lawmakers must bear in mind, even as they balance other important value judgments affecting the health and income security of millions of Americans, that the current repeal-and-replace effort represents a unique, fleeting opportunity to accomplish essential fiscal corrections.

Three factors contribute significantly to widespread confusion about the ACA’s damaging...