In a letter to Senate Majority Leader Mitch McConnell (R-Ky.), Senate Minority Leader Charles E. Schumer (D-N.Y.) outlined a number of procedural demands that Democrats say would make the Senate trial fair and able to be completed “within a reasonable period of time.”

That includes subpoenas issued by Chief Justice John G. Roberts Jr. for acting White House chief of staff Mick Mulvaney; Robert Blair, a senior adviser to Mulvaney; former national security adviser John Bolton; and Michael Duffey, a top official at the Office of Management and Budget. Mulvaney, Blair and Duffey had been subpoenaed by the House committees and defied the summons; Bolton has not been subpoenaed but indicated he would fight one in court.

“The trial must be one that not only hears all of the evidence and adjudicates the case fairly; it must also pass the fairness test with the American people,” Schumer wrote to McConnell in the letter sent Sunday. “That is the great challenge for the Senate in the coming weeks.”