In early proceedings, Roberts made it clear that he will not exercise that power unbidden. Nothing, however, prevents the House managers from making motions—either orally or in writing—to force the chief justice to take a stronger hand in the proceedings. And the Democrats have nothing to lose by trying.

Jane Chong: John Roberts’s Surprisingly Straightforward Task Ahead

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.

The notion of the chief justice as a purely ceremonial participant in impeachment trials is difficult to square with the Constitution, Senate rules, or the historical record. In other impeachment trials, for federal judges and administration officials, the Constitution dictates that the vice president serves as the presiding officer of the Senate. The Framers were plainly concerned about the conflicts of interest that would result if the person who would ascend to the presidency upon the removal of a president also presided over the trial. If the job exercised no substantive power, the Framers wouldn’t have taken care to keep the vice president out of it.

Legal scholars have rightly argued that a Senate impeachment trial is different from a judicial one. But when the Framers set up the impeachment process in Article I of the Constitution, they nevertheless had a specific idea of what a trial was: a proceeding involving evidence and disputed questions of fact. The Sixth and Seventh Amendments to the Constitution, ratified a few years after the original Constitution, protect the rights of those involved in criminal and civil cases. Taken together, these amendments describe trials with witnesses, acknowledge the possibility of compelling testimony from witnesses, and recognize the role of juries as settling factual disputes.