The rollout of the Affordable Care Act, aka Obamacare, was a "debacle" and President Obama has taken heat for repeatedly telling Americans "if you like your plan you can keep it."

That claim turned out to be false and the president's poll numbers tumbled. But the president's other big claim -- about "bending the cost curve" -- is turning out better than even one of the act's biggest supporters would've guessed.

"The cost story is better than I expected," says Peter Orszag, former director of the Congressional Budget Office and director of the Office of Management and Budget during President Obama's first term.

"At time the legislation passed, the conventional wisdom said 'this thing solves coverage but does nothing on costs,'" he recalls. "The experience since suggests the coverage part was a little rockier than people expected but the cost story turned out much better than anyone could have anticipated at the time."

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Orszag, currently vice chairman of Corporate and Investment Banking at Citigroup, cites the CBO's  decision to reduce the nation's 10-year deficit forecast by $1.2 trillion because of the slowdown in the rate of health care costs.

"There's a whole variety of evidence that's accumulating suggesting that the cost curve is indeed bending," he says. "Whether it continues to be bent remains to be seen, but we're now going on five-plus years in which cost growth has been much lower than historical levels."

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To be sure (and to be clear), Orszag doesn't attribute all of the recent decline in health care costs to the Affordable Care Act. But he does think the act's "directional" shift away from fee-for-service payments and toward accountable care organizations -- along with penalties for high readmission rates -- has pushed the industry to adopt and adjust. "I almost don't care what's causing it because if it's sustainable it massively changes things for the better," he says.

Indeed, Orszag cites a "little factoid": If Medicare costs continue to grow at the same rate per beneficiary as the average of the past five years, "there's no increase in Medicare as a share of GDP despite the coming retirement of Baby Boomers, the entire long-term fiscal gap in that program disappears and therefore most of the long-term fiscal gap facing the nation disappears."

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Orszag isn't predicting this halcyon outcome but says policymakers "should be doubling down on trying to get as close to that outcome as possible" rather than bickering over short-term and (relatively) small potatoes in the federal budget.

"We should be focused on reinforcing that slower growth in healthcare costs," he says. "That is the first order importance and everything else is a footnote."