More than five years ago, the Affordable Care Act—what most of us call Obamacare—was passed into law with two big declared goals: to reduce the number of Americans who lack health insurance and to cut health spending that doesn’t give good value for money. Has the law been a success? The country is sharply divided. The most recent Gallup and Kaiser Family Foundation tracking polls show public opinion almost evenly split, with Democrats largely supporting the law and Republicans opposing it. This partisan divide in public opinion has changed little since 2009, when President Barack Obama won a narrow victory in Congress...