There’s little question that what’s ultimately driving the nation’s long-term debt is entitlement spending—in particular spending on Medicare. Yet as the fiscal cliff negotiations have dragged on, many prominent Democrats and liberal analysts have made it clear that they oppose any and all reductions to Medicare’s benefit structure. They also argue that we ought to wait and see if a slew of promising health care cost-control measures passed in recent years work out, obviating the need for additional reforms. Jonathan Cohn of The New Republic, for example, recently asserted that such cost-cutting “is already underway thanks to the Affordable Care Act,” a law Cohn described as “arguably the most ambitious effort to reduce the cost of medical care in history.”

The most ambitious cost-control effort ever? As Senior Editor Peter Suderman observes, that’s a low bar to begin with. And at least one of Obamacare’s own authors has described the law differently. But what’s even more important, Suderman writes, is that we already have a fair amount of evidence about the efficacy of the Obama era’s cost-control measures. And so far, it’s not very promising.