The biggest threat to President Obama's healthcare reform plan is both widely overlooked and absolutely fundamental. The measure aims to vastly increase healthcare coverage while effectively freezing the ranks of the already-busy providers needed to furnish all those extra check-ups, cancer screenings and angioplasties: America's physicians. The looming doctor shortage creates three unintended forces bound to block the objectives the plan is designed to achieve. First, Medicare and Medicaid patients will increasingly face long waits to see a doctor, if they can find a physician to treat them at all. Second, people who need care urgently will flood already overloaded emergency rooms, just the scenario the plan is trying to avoid. Third, the tight restrictions on the number of physicians make it extremely difficult for insurers to find HMOs or medical groups craving new business, and hence willing to accept deep discounts in exchange for new patients.