Challengers of the Affordable Care Act are using two-year-old video footage to argue that only people who buy health insurance through state exchanges, not federal exchanges, are allowed tax credits toward their premiums. The Competitive Enterprise Institute unearthed a video from 2012 showing Jon Gruber, an MIT economist often referred to as the Affordable Care Act’s architect, telling an aide that “if you’re a state and you don’t set up an exchange, that means your citizens don’t get their tax credits.” The year the law passed, only 16 states opted for their own exchanges and only 14 opened in October 2013. Gruber later said that the remark was “just a mistake.”