Medicaid is under assault these days from nearly every direction. Governors complain that they cannot afford to put up their share of the money. Congressional Republicans led by Paul Ryan want to reduce the federal contribution by $771 billion over the next decade and shift more costs to the states and low-income Americans. President Obama has expressed willingness to cut Washington’s contribution by $100 billion over that period to help reduce the deficit.

Meanwhile, conservative critics of Medicaid — and of health care reform’s requirement to expand it — have made the outlandish claim that it provides such poor care that enrollees would be better off having no coverage.

They cite a few studies that seemed to show that, in some cases, patients on Medicaid had worse outcomes than those without any insurance. They claim this is because Medicaid pays so poorly that many doctors refuse to treat the patients, who are then unable to get care or go to the least-skilled doctors.

Those claims have now been refuted by a new study of Oregon’s program, conducted under the leadership of Katherine Baicker, a Harvard health economics professor who was an adviser to President George W. Bush, and Amy Finkelstein, an economics professor at M.I.T. It found that Medicaid patients reported both better health and more financial stability than uninsured poor people.