What started out as a solitary quest for justice by a veteran Orange County, Calif., obstetrician who was terminated without cause from two HMO networks operated by Metropolitan Life Insurance, has now blossomed into a major policy debate that has physician groups lining up to plead their global causes to the Supreme Court. And though Louis Edgar Potvin, M.D., a former president of the Orange County Medical Association, never expected to become the standard bearer for the medical profession, the case has grown beyond a mere effort by one physician to restore his practice and life savings; it has become symbolic of the increasingly heated debate that has enveloped the delivery of health care.