'What we're facing is a test of citizenship': Jon Meacham on the state of the nation

As we prepare to celebrate our country's 249th birthday, we are getting new insight into what Americans think about where the country stands. A new NPR PBS News mayor's poll found 34 of Americans feel that democracy is under serious threat and see politically motivated violence as a major problem. So, who better to talk about this moment in time than presidential historian John Meechum.He wrote a new introduction to Random Houses's volume of the Declaration of Independence and the Constitution. So, John, um ...