>> reporter: the problem is the president did just that. threaten a shutdown over border security just one day ago. >> i would shut it down over this issue. >> reporter: visiting the white house, defense secretary james mattis said a shutdown would harm security. >> it paralyzes everything we do if we go into that. >> reporter: the white house is grappling with the turmoil in the west wing as a key aide close to the president's staff secretary rob porter suddenly resigned over charges of domestic violence. two ex-wives accused himself of abuse in the marriage. this was flagged during the security process. as about the status, sarah sanders confirmed his departure. >> he is going to be leaving the white house. it won't be immediate. >> reporter: the white house release ad statement from porter that reads, these outrageous allegations are simply false. i took the photos given to the media nearly 15 years ago and the reality behind them is nowhere close to what is being