The Medicare program faces a serious challenge: it must find ways to control costs but must do so through a system of congressional oversight that necessarily limits its choices. We look at one approach to prudent purchasing - competitive pricing - that Medicare has attempted many times and in various ways since the beginning of the program, and in all but one case unsuccessfully due to the politics of provider opposition working through Congress and the courts. We look at some related efforts to change Medicare pricing to explore when the program has been successful in making dramatic changes in how it pays for health care. A set of recommendations emerges for ways to respond to the impediments of law and politics that have obstructed change to more efficient payment methods. Except in unusual cases, competitive pricing threatens too many stakeholders in too many ways for key political actors to support it. But an unusual case may arise in the coming Medicare fiscal crisis, a crisis related in part to the prices Medicare pays. At that point, competitive pricing may look less like a problem and more like a solution coming at a time when the system badly needs one.