Judy Woodruff:

And now back to the fallout over a top White House aide's resignation in a domestic abuse scandal.

There are evolving accounts from the White House on the timeline of the background investigation into former White House Staff Secretary Rob Porter, after FBI Director Robert (sic) Wray offered his own today.

To help us understand how it's all supposed to work, we are joined by Mark Zaid. He's a Washington, D.C., lawyer who specializes in security clearances.

Mark Zaid, welcome to the "NewsHour."