On average, the specialties with the highest salaries tend to have the most Republicans.

Salary  $200k-$450k

The New York Times:

In surgery, anesthesiology and urology, for example, around two-thirds of doctors who have registered a political affiliation are Republicans. In infectious disease medicine, psychiatry and pediatrics, more than two-thirds are Democrats.

The conclusions are drawn from data compiled by researchers at Yale. They joined two large public data sets, one listing every doctor in the United States and another containing the party registration of every voter in 29 states.

Eitan Hersh, an assistant professor of political science, and Dr. Matthew Goldenberg, an assistant professor of psychiatry (guess his party!), shared their data with The Upshot. Using their numbers, we found that more than half of all doctors with party registration identify as Democrats. But the partisanship of physicians is not evenly distributed throughout the fields of medical practice.