With the end of the Obama administration on the horizon, Republican presidential candidates—and members of Congress—are proposing ways to replace or repair the Affordable Care Act. Undoing the damage of ObamaCare may finally become a realistic possibility.

For now, Americans are experiencing the law’s natural consequences: rising health-insurance premiums and limitations on individuals’ choice of physicians and hospitals. Further consolidation in the insurance industry and among providers will likely drive health-care costs...