In addition to Bolton and Mulvaney, Senate Democrats have also called for testimony from Michael Duffey, an official at the White House Office of Management and Budget, and Robert Blair, assistant to the president and senior adviser to Mulvaney. The White House has repeatedly blocked witnesses from testifying.
Schumer (D-N.Y.) and Senate Majority Leader Mitch McConnell (R-Ky.) remain at an impasse over the terms of the forthcoming Senate impeachment trial. While Democrats want to decide on witnesses at the outset of the trial, Senate Republicans in recent weeks have held off deciding on witnesses until after the House managers — the lawmakers House Democrats pick to act as prosecutors — and the president present their cases. Speaker Nancy Pelosi has said she will not send over the articles of impeachment until she knows the trial details.