Some geographic areas would be hit particularly hard. A single hospital system is by far the biggest employer in many post-manufacturing cities like Pittsburgh and Cleveland. Hospitals and hospital corporations make up the top six employers in Boston and two of the top three in Nashville. Hartford is known as the insurance capital of the world. Where would New Jersey be if drug makers took a big hit, or Minnesota if device makers vastly shrank their work force? (That may be why some Democratic representatives and senators from these left-leaning states have been quiet or inconsistent on Medicare expansion.)

Stanford researchers estimate that 5,000 community hospitals would lose more than $151 billion under a Medicare for all plan; that would translate into the loss of 860,000 to 1.5 million jobs. A Navigant study found that a typical midsize, nonprofit hospital system would have a net revenue loss of 22 percent.

Robert Pollin, an economist at the Political Economy Research Institute of the University of Massachusetts, Amherst, is frustrated not just by the doomsday predictions but also by how proponents of Medicare for all tend to gloss over the jobs issue.

“Every proponent of Medicare for all — including myself — has to recognize that the biggest source of cost saving is layoffs,” he said. He has calculated that Medicare for all would result in job losses (mostly among administrators) “somewhere in the range of two million” — about half on the insurers’ side and half employed in hospitals and doctors’ offices to argue with the former. Supporters of Medicare for all, he said, have to think about a “just transition” and “what it might look like.”

Of course, if more people get health insurance under an expanded Medicare, there will be a greater need for some workers — like nurse practitioners and physician assistants. And there is a large unmet labor need in caring for an aging population. The latter are mostly low-wage jobs, however, and neither compensates for the losses.

Dr. Pollin suggests that a transition to Medicare for all should be accompanied by a plan to give those made redundant up to three years of salary and help retraining for another profession.

Despite the short-term suffering caused by any fundamental shift in our health care delivery system, reform would ultimately redirect resources in ways that are good for the economy, many experts say.