The NEJM recently reported on physician views about the public option and the possible expansion of Medicare. It turns out, most physicians favor the status quo of a mix of public and private financing.
Why would doctors support a public plan? It could be ideological. They may simply believe that more government health insurance would make society more equitable. Or they may believe that they can receive more money from government reimbursement than hard-bargaining private companies. Or it could be that dealing billing rules from multiple private insurance companies is much worse than dealing with billing issues from Medicare.