 CBS News special report, best-selling hillbilly elegy author and former Trump critic, Senator J.D. Vance, introduced himself as Donald Trump's running mate on the third night of the Republican National Convention. There's still so much talent and grit in the American heartland. But for these places to thrive, my friends, we need a leader who fights for the people who built this country. CBS's Margaret Brennan is at the convention in Milwaukee. Her take on the GOP vice presidential nominee. He's saying...