A key figure in President Trump's 2016 campaign and a former White House adviser, Steve Bannon remains an outspoken champion of the MAGA movement and has courted far-right parties in Europe. He talks with "Sunday Morning" senior contributor Ted Koppel about Trump's place in history; the influence of Nazi propaganda filmmaker Leni Riefenstahl on his productions; and why he believes a Republican victory in the midterms is imperative.