The nation’s largest doctor group narrowly defeated a measure Tuesday that would have ended their opposition to proposals that would allow the government to fully finance the U.S. healthcare system.

The group, the American Medical Association, will instead continue to back an expansion of Obamacare and begin to study “public option” approaches in which government coverage is offered to people alongside private health insurance plans. The plan it rejected is often referred to as “single payer,” and in Congress it is embodied in the Medicare for All Act.