Half a century ago, the creation of Medicare and Medicaid was a triumph of American egalitarianism. Within a decade, the United States went from a country where 1 in 3 people lacked health insurance to a nation where just 1 in 10 went without coverage.

President Barack Obama has similar ambitions for the Affordable Care Act, which launches this week with marketplaces that will allow Americans to choose among competing insurance plans.

"Obamacare," as it is known, certainly will increase access to health care across racial and class lines. Yet the program's success relies on the cooperation of two dozen conservative-leaning states that are home to half of the nation's 50 million uninsured. In many of these states, the public tends to oppose the law, and politicians are doing all they can to undermine it. If they succeed, the dawn of the Affordable Care Act (ACA) may create new disparities in health coverage between the states that embrace Obamacare and those that resist it.