With Roberts looking on, the White House counsel, Pat Cipollone, lied on the Senate floor by claiming, among other things, that House Intelligence Committee Chairman Adam Schiff hadn’t allowed his Republican colleagues into a secure meeting room during the proceedings that led up to Trump’s impeachment. This was untrue but went unchallenged in the moment. When things got heated between Cipollone and House Judiciary Committee Chairman Jerry Nadler—who bemoaned a Republican cover-up—Roberts merely stated, “I think it is appropriate at this point for me to admonish both the House managers and the president’s counsel in equal terms to remember that they are addressing the world’s greatest deliberative body.”
In a courtroom, a comment as demonstrably false as Cipollone’s would likely be met with a motion to strike the misstatement from the record. Roberts—who cares deeply about the legitimacy of the Supreme Court and of the entire judicial branch, which he leads—would be hard-pressed to rule outright that lies are acceptable in any trial over which he is the presiding officer.
Similarly, nothing prevents the House impeachment managers, whom Schiff leads, from filing motions and legal briefs laying out their positions on the admission of evidence and other matters. The chief justice would have to do something with them. Any decision by Roberts to punt a disputed matter without a ruling—to a full Senate run by a declared Trump partisan, no less—would be hard for him to portray as merely staying above the political fray.