If only Halloween hadn’t passed, someone could go as MIT’s Jonathan Gruber. He is the economist most likely to get people in Washington to run out of a room. At the moment he is a problem for the Obama administration and Democrats, though he’s spooked Republicans before, too. At an academic panel in 2013, Gruber said of the Affordable Care Act: “This bill was written in a tortured way to make sure” the Congressional Budget Office “did not score the mandate as taxes.” He also said that “lack of transparency is a huge political advantage,” and added, “Call it the...