And though the political polarization of specialties has grown over the last two decades, all are trending left, with less than 50 percent of physicians' donations overall now going to Republicans.
The authors attributed much of the trend to gender and income. There has been an influx of female doctors, with more going into lower-paying specialties such as pediatrics.
The findings "suggest that the polarization of physician contributions relates to their economic status; physicians in specialties with higher earnings are more likely to contribute to Republicans than those with lower earnings," the researchers wrote last week in JAMA Internal Medicine.
The pattern went well beyond pediatricians and surgeons; GOP donations tracked almost exactly with incomes of nearly 50 specialties.
Still, money is not the only difference between practice areas. Pediatricians, infectious-disease, and internal-medicine doctors, all on the low end of the pay scale, may be more likely to see the impact on their patients of poverty and unemployment.
"You are confronted every day with those issues, and realize that you are powerless, that you can't write prescriptions for food, for jobs, for better housing," said Gene Bishop, a retired Philadelphia internist.
The high-end specialists "are not asking people about the nitty-gritty of their lives," said Bishop, who was not involved with the study. "They are [more] procedure-oriented."
Increased recognition of the influence of social factors may play a role in another of the study's findings: political contributions by physicians increased nearly tenfold between 1992 and 2012, much more than the 6.5-fold rise in donations from the public.
"As the Affordable Care Act legislation played out starting in 2009," said Valerie Arkoosh, the anesthesiologist who ran unsuccessfully in last month's Democratic primary in Pennsylvania's 13th Congressional District, "there was a growing awareness of physicians in this generation of the importance of the political process in health care."
Arkoosh believes that regardless of physicians' stands on the federal health-care overhaul, they saw that "the Democratic Party was more willing to engage in solutions" while the GOP offered "more of the status quo."
The study, however, found two blips in the long-term trend toward Democrats: donations from doctors declined during the debates on "Hillarycare" in 1994 and "Obamacare" in 2010.
Meanwhile, physicians serving in politics still are much more likely to be Republicans - 16 of the 20 now in Congress. Most are specialists, which may have provided the necessary finances to mount a campaign.
"At present," the paper concludes, "all that is certain is that in political terms, the profession is in play."