Glenn Kessler is the head of the Fact Checker staff of the Washington Post. Along with Salvador Rizzo and Meg Kelly, he is the author of the new book, "Donald Trump and His Assault on Truth: The President's Falsehoods, Misleading Claims and Flat-Out Lies." It is a compilation and distillation of the 19,000 false or misleading statements Donald Trump has made and the Washington Post has documented in its mammoth database of presidential untruths since the president took office. Kessler spoke with Benjamin Wittes about what makes Trump different from other presidents, the task of documenting the president's lack of candor on a daily basis and what it all means to have a president who lies this much.