Abstract:The 2010 Patient Protection and Affordable Care Act (ACA) passed through Congress on partisan lines and with only lukewarm public support. The Obama administration and Congressional Democrats, though, had reason to expect that the ACA's political fortunes would substantially improve as the acrimonious debate over its enactment faded and millions of Americans came to receive significant benefits from health care reform. But 5 years after its passage, the ACA's political foundations remain shaky. We suggest that one reason for the ACA's unsettled fate is the role of policy feedbacks that undermine public support for and opponents' acceptance of the program. The ACA experience highlights how policy feedbacks can vary widely in their political impact, and suggests that some policies are in fact self-undermining. We also emphasize the crucial role of partisan polarization as a mediating factor in shaping policy feedbacks.