Large hospital systems and trade groups have vociferously criticized Democrats' "Medicare for All" proposals, but rural facilities and public hospitals that treat mostly low-income patients are sitting on the sidelines of the debate.

Why it matters: Safety nets and many rural hospitals could hypothetically benefit under Medicare for All, but expressing support would put them at odds with their larger brethren.

Between the lines: The Partnership for America's Health Care Future has become one of the loudest industry-funded voices against Medicare for All.

Pharmaceutical companies, health insurers and others are part of PAHCF. But 10 hospital systems and lobbying groups, like Ascension and the American Hospital Association, drive PAHCF.

Chip Kahn, the head of the Federation of American Hospitals, said PAHCF was his "brainchild," according to Modern Healthcare.

Yes, but: Some hospital constituencies aren't part of the anti-single-payer lobbying.

America's Essential Hospitals, the trade group for safety net hospitals, and the National Rural Health Association, which represents rural hospitals and providers, are not part of PAHCF. They also don't have official positions on Medicare for All.

A spokesperson for AEH said the group recognizes industry peers "have raised reasonable questions" about Medicare for All, but "our focus right now is where our members want it: on stopping the $4 billion cut" to supplemental Medicaid payments.

"With specific legislation not moving forward at this time, I don't see us weighing in anytime soon," NRHA CEO Alan Morgan said. "I don't see us at odds. We just haven't entered the national debate yet."

In an interview, Kahn would not discuss on the record why those two groups were not part of PAHCF.

The big picture: Hospitals that mostly care for poor and uninsured patients could see higher, more stable revenues if everyone had Medicare — a program that often pays higher base rates than Medicaid and infinitely higher rates than nothing at all.

Cook County's public hospital system in Chicago, for instance, gets 79% of its gross patient revenue from the uninsured and Medicaid. That system and multiple other hospitals did not respond to interview requests.

Separately, Medicare pays rural "critical access" hospitals 101% of their allowable costs, although those payments have suffered since Congress instituted mandated cuts in 2013.

The intrigue: "If you're trying to solve the problem that we want to get everybody covered and we want to level the playing field between the hospitals that take care of the poor people and hospitals that take care of the rich people, Medicare for All is something we better take a look at," Eric Dickson, CEO of UMass Memorial Health Care, told Politico.