(CNN) The American Medical Association is coming under increasing fire for opposing "Medicare for All."

Energized by the growing attention on universal health care in the 2020 presidential campaign and in Congress, medical students, nurses and other activists are expected to rally Saturday at the AMA's annual meeting in Chicago to urge its leadership to change its position.

Nearly two dozen groups -- including those representing doctors, nurses, medical students and other health care workers -- are participating in the campaign, organizers say.

The influential association has long opposed a government-run health care system, such as the Medicare for All proposal championed by Vermont Sen. Bernie Sanders, an independent running for the Democratic presidential nomination. It is also a member of the Partnership for America's Health Care Future , a coalition of health industry groups seeking to quash any momentum behind Medicare for All.

The rally comes as the AMA doubles down on its opposition to universal health care. After being pressed to review its position by its medical students caucus at last year's meeting, the association recently reaffirmed its commitment to strengthening the Affordable Care Act and making coverage more affordable, in part by increasing the eligibility and amount of federal subsidies for premiums and out-of-pocket expenses.

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