This article is from the archive of our partner National Journal

When Sen. Ted Cruz timed his presidential announcement earlier this week to the fifth anniversary of the Affordable Care Act, his fondest hope was that the law would not survive for many more. "Imagine in 2017," Cruz declared, "a new president signing legislation repealing every word of Obamacare."

Sen. Ted Cruz speaks during the "Exempt America from Obamacare" rally, on Capitol Hill, September 10, 2013 in Washington, D.C. (Drew Angerer / Getty Images)The determination among conservatives to uproot the ACA is strikingly undiminished five years after President Obama signed it into law. But the context for their crusade is shifting. Defying opponents' predictions, and its own early stumbles, the law is now contributing to a virtuous cycle generating gains in coverage, cost, and quality across the health care system. The critical question for the future may be whether those positive trends build enough of a constituency to protect the law by 2017, when Republicans could win the unified control of the White House and Congress they will need to undo it.

The war over the ACA has already outlasted the skirmishing that followed passage of America's other key safety-net programs. In 1936, Republican presidential nominee Alf Landon ran on repealing the Social Security Act, signed one year earlier. But after Landon won just two states, Wendell Willkie, the 1940 GOP nominee, embraced the program. Neither congressional Republicans nor Richard Nixon, the party's 1968 presidential nominee, sought to repeal Medicare after Lyndon Johnson signed it in 1965. And while some states initially resisted joining Medicaid, that opposition melted quickly.

By contrast, House Republicans voted again on Wednesday to repeal the ACA, and Senate Republicans will likely soon follow. Twenty-two states with either Republican governors, GOP legislatures, or both are still refusing to accept the funds the law provides to expand Medicaid to the uninsured. (Even when Republican governors in Tennessee, Utah, and Wyoming recently proposed to expand Medicaid, GOP state legislators said no.) Few would be surprised if every 2016 GOP presidential contender endorses repeal.

Beyond these political challenges, the law faces an existential legal threat in the Supreme Court case brought by a conservative think tank (joined by six Republican state attorneys general) that aims to invalidate the subsidies provided to the uninsured in the 34 states that did not establish their own health exchanges. (Those states, almost all controlled by Republicans, rely on the federal website.) Although oral arguments highlighted holes in the challengers' case, the administration must still win support from at least one Republican-appointed justice—or the Court will revoke subsidies from an estimated eight million people, potentially destabilizing the law.

(RELATED: How the 2016 Republicans Will Fight Over the Future of Obamacare)

This hostility to the ACA has become impervious to contrary evidence. Like all major federal legislation, the law has exhibited flaws and produced unintended consequences. But, by any reasonable accounting, it is contributing to an array of positive health care trends.

Since Obama signed the law, the number of Americans lacking health insurance has declined by 16.4 million. That's fewer than advocates hoped, but it has still reduced the share of uninsured Americans by more than one-third. In a 2014 survey by the nonpartisan Commonwealth Fund, three-fourths of the newly insured said they were satisfied with their coverage. Fourteen million fewer adults in 2014 than 2012 said they deferred needed care because they couldn't afford it, the survey found.

From 2011 to 2013, federal figures show, per capita health expenditures grew at the slowest rate ever recorded; although cost growth ticked up in 2014, largely because of rising drug expenses, the long-term trends remain promising. "It's hard to be wildly optimistic," says Len Nichols, director of George Mason University's Center for Health Policy Research and Ethics, "but I do think we've bent the [cost] curve, and there is momentum in our direction." Premiums for employer-provided insurance rose nearly 40 percent less from 2011 to 2014 than they had in the previous three years. In the ACA exchanges, premiums increased minimally in year two, largely because 25 percent more insurers participated. The exchange markets "show significant stability," says Caroline Pearson, senior vice president of consulting firm Avalere Health.

Total cost estimates for implementing the ACA have plummeted. At the same time, quality is improving: Studies have found steady declines in both hospital-acquired illnesses and hospital readmissions since the law's passage. In states that expanded Medicaid, doctors are diagnosing more diabetes cases early, too—ensuring cost-savings and better health later.

The law isn't solely responsible for these trends. But with provisions that range from penalizing hospitals for substandard care to rewarding coordination between doctors, it has accelerated a critical shift toward linking physician compensation to the standard—not just the volume—of care. The law's initial experiences offer promise that expanding access, restraining costs, and improving quality can be complementary, even reinforcing, goals.

In a rational political system, Americans would be debating how to improve the law and smooth its inevitable bumps (like overly restrictive coverage networks). Instead, we remain trapped in a theoretical debate increasingly disconnected from the law's actual impact. The ACA's survival beyond President Obama may depend on whether ideology or Americans' experience with the law counts more in deciding its fate.

This article is from the archive of our partner National Journal.

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