Mulvaney looks to join lawsuit fighting impeachment probe subpoena

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Acting White House Chief of Staff Mick Mulvaney is looking for a court to tell him whether or not he should testify before lawmakers in the impeachment probe. Katy Tur discusses with Politico Senior Legal Affairs writer Josh Gerstein, and author of “The Gatekeepers: How the White House Chiefs of Staff Define Every Presidency” Chris Whipple.