Nearly 4 million Americans lack health insurance because of a 2012 Supreme Court decision that allowed states to opt out of the Affordable Care Act’s Medicaid expansion. In the coming weeks, Congress has a chance to clean up the mess the court’s decision created.
To understand what Congress can do now, it is useful to review how we got here. The Affordable Care Act required all state Medicaid programs to cover people with incomes up to 138 percent of the poverty line (currentl...