Mulvaney asks to join lawsuit over conflicting demands for impeachment testimony

Acting White House chief of staff Mick Mulvaney on Friday asked to join a federal lawsuit seeking a judicial ruling on whether Congress can compel President Trump’s senior advisers to testify in the impeachment inquiry.

The lawsuit was originally filed late last month by Charles Kupperman, a former top national security aide to Trump, who said he faced conflicting orders from House Democrats and the White House over whether he must participate in the investigation and needed the court to tell him what his constitutional duty was.