In the week preceding the release of Bernie Sanders’s Medicare for All bill, the Vermont senator’s office was flooded with calls — so many, in fact, that the legislative aides on the other line often guessed callers’ purpose before being prompted. At issue was whether the single-payer health care system Sanders’s bill envisions should include copayments, out-of-pocket payments for health services at the point of care.

For the single-payer advocacy group Physicians for a National Health Program (PNHP), the answer was a resounding “no.” So upon discovering that copays remained in Sanders’s penultimate draft, they sprang into action. After a week of open letters, tweets and appeals from like-minded organizations, Sanders ultimately struck copays from the bill’s final version.

Earlier versions of Sanders’s bill probably included copays for doctors visits and prescription drugs for the same reason that economists like them: they drive down health care usage and costs. After all the attacks branding Sanders’s relatively pedestrian social-democratic platform as fantastical promises of ponies for all, perhaps Sanders’s legislative aides believed meager copays gave their proposal an air of seriousness.