President Obama hasn’t proposed increasing the eligibility age for Medicare. But would he agree to do so, in order to secure a broader agreement that raises taxes on the wealthy and avoids the automatic spending cuts set to take effect on January 1? Liberals are worried that he will—thanks in part to a pair of recent columns, one each by my friends Jonathan Chait and Ezra Klein.

Under the provocative headline, “Go Ahead, Raise the Retirement Age,” Jon argued that Obama would eventually have to make some sort of concession—and that, all things considered, making people wait a little longer to enroll in Medicare was the least unappealing option. Ezra suggested that the outlines of a compromise were coming into view, with Obama conceding on a higher Medicare age in exchange for somewhat higher taxes on the wealthy. The columns have provoked spirited, sometimes angry responses from fellow liberals. Responding to Jon, David Dayen wrote, “The idiocy on display here can hardly be believed.” (Jon then responded here.)

It might look like just another liberal food fight. It’s not. The issue here is very real. Obama has been crystal clear about his demands in this debate. Tax rates on high incomes must go up. The debt ceiling drama has to end. He has made no similarly ironclad statements about the Medicare age. Obama would prefer to reduce Medicare spending by continuing to reform the way it pays for goods and services. He's even proposed a series of such reductions. But if it took more to get the concessions he wants from the Republicans? If it took something else to get what he thinks is a major deal on fiscal policy? Under those conditions, Obama would probably agree to a higher Medicare age—just like he did in 2011, when he was negotiating with House Speaker John Boehner over how to increase the debt ceiling. "The president put it on the table once before," says a senior Democratic aide on Capitol Hill. "I wouldn't be surprised if he did it again."

The idea made me queasy back then. And it makes me queasy now. As both fiscal and health care policy, increasing the Medicare age from 65 to 67, even gradually, has very little to recommend it. The federal government would save money, yes, but only because state governments, employers and individual seniors would pay more. Overall, the nation would end up spending more on medical care, not less. That’s the very opposite of what public policy, including Obamacare, is trying to achieve.

That shortcoming has gotten a lot of attention lately. Here's what hasn't: The distributional effects of a higher Medicare age, although that's partly because the effects are complicated to sort out. According to the best available study, which comes from the Kaiser Family Foundation, 65- and 66-year-olds with incomes of less than 250 percent of the poverty line, or about $30,000 for a couple, would generally end up paying a little less in out-of-pocket medical expenses if the Medicare age went up. That’s because they’d likely end up getting insurance from Medicaid or through one of Obamacare’s insurance exchanges, which, at those low income levels, would offer better financial protection. So far, so good.