America is divided — and that's by design

It used to be said that you could have your own opinion, but you couldn't have your own facts. But after decades of deliberate effort by some conservative Republicans to undermine public trust in government, the media and even in science, agreement about facts and even about the rules of the game in American democracy is not what it used to be. How did we get here? Thomas Mann, a senior fellow at the Brookings Institution, and co-author of "It's Even Worse Than it Was: How the American Constitutional System Collided with the New Politics of Extremism" weighs in.