Numerous forecasts have predicted shortages of primary care providers, particularly in light of an expected increase in patient demand resulting from the Affordable Care Act. Yet these forecasts could be inaccurate because they generally do not allow for changes in the way primary care is delivered. We analyzed the impact of two emerging models of care--the patient-centered medical home and the nurse-managed health center--both of which use a provider mix that is richer in nurse practitioners and physician assistants than today's predominant models of care delivery. We found that projected physician shortages were substantially reduced in plausible scenarios that envisioned greater reliance on these new models, even without increases in the supply of physicians. Some less plausible scenarios even eliminated the shortage. All of these scenarios, however, may require additional changes, such as liberalized scope-of-practice laws; a larger supply of medical assistants, licensed practical nurses, and aides; and payment changes that reward providers for population health management.