THE OBAMACARE debate has been out of whack from the start. Republicans have criticized the wrong things, allowing Democrats to ignore the Affordable Care Act's biggest flaws. Now, this off-kilter debate may lead to the quiet loss of one of the law's most important provisions, currently on Congress's chopping block.

The partisan conflict has mostly focused on Obamacare's health-care-coverage expansion, and Democrats have won that argument. The GOP's recent repeal-and-replace fiasco revealed that Americans are mostly comfortable with assertive government regulation and spending in order to guarantee (nearly) all Americans affordable, comprehensive coverage. Though they tried to make it sound otherwise, Republicans countered with policies that would have shredded this guarantee, particularly for the neediest. They failed.

The problem is not that Obamacare's coverage expansion was fundamentally flawed, as Republicans have alleged. It is that it was not accompanied by measures to control costs across the health-care system, which has gotten so expensive it represents a sixth of the economy. And that is just for now: With the baby boomers aging, and tantalizing but expensive medical innovations on the horizon, costs threaten to rise unsustainably if the government does not force changes to the way care is delivered.

The right response is not to cut poor and sick people off insurance rolls but to stop paying for treatments and services that are unneeded, that do not work or that are not any better than cheaper alternatives. This is hard, because it involves telling people to change — and occasionally saying "no." So Democrats mostly avoided the issue when they wrote Obamacare.

Mostly, but not entirely. They tucked in a few cost-cutting provisions, significantly raising Obamacare's appeal to those who worried about expanding coverage without encouraging more responsibility on health-care spending. The most important was the creation of the Independent Payment Advisory Board (IPAB), a panel of experts tasked with making some hard choices. If health-care spending accelerates too rapidly, the board must recommend ways to slow the rise through changes to Medicare's payment system — without slashing benefits. The board's conclusions would go to Congress, which would have the opportunity to overrule the experts. If lawmakers declined to do so, the board's recommendations would automatically take effect.

The idea was to ensure that costs did not escalate too quickly by removing political barriers to ­efficiency-driving reforms. Recent history has shown that, when the issue is left to Congress, doctors and patient groups will effectively block reform, even if the evidence suggests current practice is misguided.

Indeed, the forces favoring complacency and waste have not surrendered. Even though costs have not yet risen fast enough to trigger the IPAB, the board has sustained heavy criticism from both sides of the aisle. Republicans say they dislike the notion of government bureaucrats dictating health payment policies. Democrats say they dislike anything that smacks of a cut to Medicare. A bipartisan bill ending the IPAB passed the House Ways and Means Committee last Wednesday.

Republicans, who claim they want to reduce wasteful government spending, should stop trying to repeal this important piece of Obamacare. So should Democrats.