The fight over health insurance exchanges epitomizes the rapid evolution of health reform politics in the decade since the passage of the Affordable Care Act (ACA). The ACA's drafters did not expect the exchanges to be contentious because they would expand private insurance coverage to low- and middle-income individuals who were increasingly unable to obtain employer-sponsored health insurance. Instead, exchanges became one of the primary fronts in the war over Obamacare. Have the exchanges been successful? The answer is not straightforward and requires a historical perspective through a federalism lens. What the ACA has accomplished has depended largely on whether states were invested in or resistant to implementation, as well as individual decisions by state leaders working with federal officials. Our account demonstrates that the states that have engaged with the ACA most consistently appear to have experienced greater exchange-related success. But each aspect of states' engagement with or resistance to the ACA must be counted to fully paint this picture, with significant variation among states. This variation should give pause to those considering next steps in health reform, because state variation can mean innovation and improvement but also lack of coverage, disparities, and diminished access to care.