Former Deputy Attorney General Sally Yates is sworn in prior to testifying before a Senate Judiciary Committee hearing on “Russian interference in the 2016 U.S. election” on Capitol Hill in Washington, U .S., May 8, 2017.

Former campaign manager Corey Lewandowski (C) says hello to reporters as he and White House advisors Sebastian Gorka (from L), Omarosa Manigault, White House Staff Secretary Rob Porter and Communications Director Anthony Scaramucci accompany President Trump for an event celebrating veterans at AMVETS Post 44 in Struthers, Ohio, U.S. July 25, 2017.

White House Communications Director Hope Hicks leaves the U.S. Capitol after attending the House Intelligence Committee closed door meeting in Washington, U.S., February 27, 2018.

U.S. Secretary of State Rex Tillerson listens as President Donald Trump holds a cabinet meeting at the White House in Washington, U.S., October 16, 2017.

U.S. President Donald Trump talks to senior staff Steve Bannon during a swearing in ceremony for senior staff at the White House in Washington, DC January 22, 2017. REUTERS/Carlos Barria

White House Staff Secretary Rob Porter (L) reminds U.S. President Donald Trump he had a bill to sign after he departed quickly following remarks at his golf estate in Bedminster, New Jersey U.S., August 12, 2017. Picture taken August 12, 2017.

White House Communications Director Anthony Scaramucci talks to the media outside the White House in Washington, U.S., July 25, 2017.

Preet Bharara, the United States Attorney for the Southern District of New York talks during a news conference to discuss alleged fraud by Russian Diplomats in New York December 5, 2013.

Health and Human Services Secretary Tom Price (R) listens to U.S. President Donald Trump speak during a meeting with health insurance company CEOs at the White House in Washington, U.S. February 27, 2017.

Rachel Brand, nominee to be Associate Attorney General, testifies before the Senate Judiciary Committee on Capitol Hill in Washington March 7, 2017.

White House Press Secretary Sean Spicer looks at a photographer during the daily briefing at the White House in Washington, U.S. June 12, 2017.

Acting FBI Director Andrew McCabe arrives to testify before the U.S. Senate Select Committee on Intelligence on Capitol Hill in Washington, U.S. May 11, 2017.

U.S. President Donald Trump hands Chief of Staff Reince Priebus (R) an executive order that directs agencies to ease the burden of Obamacare, after signing it in the Oval Office in Washington, U.S. January 20, 2017. Also pictured is White House Staff Secretary Rob Porter (C).

White House National Security Advisor Michael Flynn (C) arrives prior to a joint news conference between Canadian Prime Minister Justin Trudeau and U.S. President Donald Trump at the White House in Washington, U.S., February 13, 2017.

Rick Dearborn, White House Deputy Chief of Staff for Legislative Affairs, departs following a Congressional Gold Medal ceremony for former Senator Bob Dole at the U.S. Capitol in Washington, U.S., January 17, 2018.

Former White House deputy assistant Sebastian Gorka speaks at the Conservative Political Action Conference (CPAC) at National Harbor, Maryland, U.S., February 24, 2018.

Trump's economic adviser Gary Cohn wipes his eye before observing a moment of silence in remembrance of those lost in the 9/11 attacks at the White House in Washington, U.S. September 11, 2017.

FILE PHOTO: Then Deputy Chief of Staff Katie Walsh (C) talks with U.S. President Donald Trump during a swearing-in ceremony at the White House in Washington, U.S., January 22, 2017.

Former FBI Director James Comey prepares to testify before a Senate Intelligence Committee hearing on "Russian Federation Efforts to Interfere in the 2016 U.S. Elections" on Capitol Hill in Washington, U.S. June 8, 2017.

John McEntee walks to Marine One to join U.S. President Donald Trump for travel to Florida in Washington, U.S., February 16, 2018. Picture taken February 16, 2018.

U.S. President Donald Trump hands the pen to Vice President Mike Pence after signing an executive order dealing with the structure of the National Security Council, in the Oval Office at the White House in Washington, U.S. January 28, 2017. Also pictured are National Economic Council Director Gary Cohn (L) and Deputy National Security Advisor K. T. McFarland (2nd R).