The most prominent question today, is shall the Senate hear witnesses? Precedent suggests the answer is “yes”– there have been 15 prior impeachment trials in the Senate (two involving Presidents) and all have had witness testimony in the Senate. And there is no Constitutional bar against witnesses in what the Constitution refers to as an impeachment “trial.” …[McConnell maintains] his constitutional oath to do “impartial justice” permits him to coordinate every aspect of trial management with counsel for the President, who objects to witnesses.

…Indeed, it is the Chief Justice of the United States who shall “preside” over the trial, not the Majority Leader. So why isn’t it up to Roberts to decide whether witnesses shall appear?

John Roberts Has the Power to Allow Impeachment Witnesses | Time

hmmm