No fancy modeling tool is required to predict Democrats’ responses to this paper. It’s a political Rorschach test. Each candidate will see what they want to see. Economist Len Nichols sees it as ammunition for candidates like Biden and Buttigieg who oppose “Medicare for all.” “I think it’s going to give credibility to those who argue there are other ways than single payer to accomplish our goals. And it’s going to challenge the credibility of those who say that only single payer can accomplish our goals,” he said.

But will single payer advocates really be slowed? “I don’t think it’s going to stop the people who are currently proponents of single payer,” said Dr. Kavita Patel, a primary care internist and former director of policy in the White House under Barack Obama. Patel said the Sanders and Warren camps will likely downplay or flat-out dispute the work. “If you’re Bernie Sanders, then you’re going to look at that—and his campaign obviously will—and they’re going to poke holes at it because it really takes aim at one of his basic principles,” she said.

Advocates looking to poke holes in these new numbers will likely start with the assumptions on which Urban’s model is built. Every microsimulation model is based on some amount of guesswork and assumptions. For example, the Urban paper predicts how many people would ditch their insurance at work, if they could get it cheaper from the federal government. To answer that, Blumberg and the team comb through academic literature looking for real world clues about how things may play out.

“Even if the analysis is run correctly, depending upon what the assumptions are, that can have massive ramifications,” said Harvard physician Adam Gaffney, President of Physicians for a National Health Program. “I am worried that we’re going to see a particularly high cost for single payer. I would like to see fair assumptions about savings and costs.” Gaffney argues that in a 2016 paper analyzing Sanders’ earlier “Medicare for all” plan, Urban lowballed how much the federal government would save by negotiating with doctors, hospitals, and drug companies. He also believes Urban shortchanged the savings that would result from a single plan requiring many fewer administrative middlemen.

Both sides do agree that “Medicare for all” would result in significant savings in some areas. Their disagreements lie in the details. Just how much would be saved and what would the consequences be? When it comes to predicting the answers to some of the biggest questions surrounding “Medicare for all,” like how much the federal government would pay doctors and hospitals, Urban’s John Holahan says there are a lot of unknowns.

“The only real way you keep costs down is by paying providers less. How much can you push hospital rates down and physician fees down without causing just massive chaos?” he said. Blumberg is also quick to admit there’s plenty we don’t know. “Can I say we’re absolutely giving you a perfect answer when these guys turn the crank and we get simulation results?” said Blumberg. “No, there’s no perfect answer. There’s always some error and uncertainty.”

Another thing Blumberg is unsure of: the impact this paper may have. Over the years, some of Urban’s papers have been forgotten before they were read. Others have helped changed the course of health policy history. The timeliness of this one seems to guarantee it at least some traction. Blumberg isn’t certain. But the work guarantees her one small satisfaction: There will be numbers.

“This is a moment where serious people are thinking about serious proposals. This is not just a math exercise,” said the economist. “This is an exercise to inform good policy, because the people underlying each of these numbers need good policy.”

Once again, Linda has gotten her work into the hands of people who can do something with it. The rest is up to them.