Health care is one of the most pressing issues in the 2020 presidential race, and most of the Democratic presidential candidates are supporting an expansion of coverage through what’s being called Medicare for All or a public option system. An overall fix for the out-of-control costs of health care is tough to craft and implement, but a series of smaller fixes could be a more feasible and effective way of dealing with the system’s problems. One such idea would be preferred pharmacy networks, a relatively new tool used by health insurers to steer consumers to pharmacies where they have negotiated lower drug prices. This cost-reduction mechanism is the focus of new research by Ashley Swanson, an applied microeconomist and professor of health care management at Wharton. She is author of “ Preferred Pharmacy Networks: Health Care Savings on the Margins ,” a brief published by the Wharton Public Policy Initiative that examines the potential savings for enrollees in Medicare Part D.…