Jonathan Gruber, the man at the center of Obamacare’s troubled public image, apologized to Congress for “glib” and “thoughtless” comments about the stupidity of the American voters and how the health overhaul passed, arguing he is no political expert and shouldn’t have posed as one in speeches around the country. “It’s never appropriate to try to make oneself seem more important or smarter by demeaning others. I knew better. I know better. I’m embarrassed, and I’m sorry,” Mr. Gruber, an economics professor at the Massachusetts Institute of Technology, told the House oversight committee chaired by Rep. Darrell Issa, California Republican.