Washington(CNN) Senate Minority Leader Schumer wrote a letter to Senate Majority Leader Mitch McConnell Sunday evening, calling for at least four witnesses to testify in a Senate impeachment trial. Those witnesses include: acting White House chief of staff Mick Mulvaney, former national security adviser John Bolton, senior adviser to the acting White House chief of staff Robert Blair and Office of Management and Budget official Michael Duffey.
Read the letter below.