How is John Kelly’s credibility hurt by Rob Porter scandal?

The White House is on the defensive after two ex-wives of a top aide said he physically assaulted them. Staff secretary Rob Porter also did not have a permanent security clearance. Why did chief of staff John Kelly initially defend Porter, and how much was known about the allegations, and for how long? Judy Woodruff talks with Yamiche Alcindor and Chris Whipple, author of “The Gatekeepers.”