Democratic support for Medicare for All is slipping from the high levels seen around the November midterm elections as voters worry about its price tag and the toll it would take on both private and employer health coverage.

The proposal seeks to provide everyone in the U.S. with access to health coverage under a federal system that would replace Medicaid, Medicare, most private insurance and employer coverage. Progressive candidates issued full-throated endorsements during campaigns for congressional and state-level elections last November. As the message resonated among voters, even some centrist candidates joined as well.

Now, enthusiasm for the proposal is waning as supporters face pointed questions over how it would work—and how it would be paid for. As a result, more candidates are backing intermediate measures, including optional buy-ins to government-run coverage that are likely more attainable in the short term.

“At the slogan level, it makes a lot of sense,” said Lara Brown, director of George Washington University’s Graduate School of Political Management. “As people start putting together a plan, and people hear about it, it’s disconcerting.”

Research pegs the proposal‘s cost at more than $30 trillion over 10 years, although supporters say it ultimately would lower overall U.S. spending on health care. Republicans and industry players, including insurers, warn the program would end the employer coverage now received by about 155 million workers. They have started opposition campaigns, including television ads.