Hope Hicks's resignation caused a stir. But what she did first is more important.

THE CAPITAL last week was seized by the news that White House communications director Hope Hicks was leaving President Trump’s side, the latest senior aide to depart a tumultuous West Wing.  Ms. Hicks’s activities just before her announcement were more potent. Testifying before the House Intelligence Committee, which is investigating Russian interference in the 2016 election, she refused to answer any questions about anything that happened after Mr. Trump was sworn in. She did not — indeed could not — invoke executive privilege, a power that only Mr. Trump can wield to prevent disclosure of information to Congress. But she refused to answer anyway, as though executive privilege properly applied.