As a White House special adviser on health policy, I was party to many of the internal debates that shaped the Affordable Care Act. Looking back, I believe that three key issues were emblematic of the sometimes tortured interplay of policy and politics in crafting Obamacare—and of the inherent difficulty of fashioning complex legislation in today's Washington.

To control costs and improve quality in health care, the White House economic team believed that we had to change the way physicians are paid. About 85% of payments...