Emerging almost from the shadows, Chief Justice John G. Roberts, Jr. delivered a stern and unexpected late night warning to Rep. Jerrold Nadler and White House Counsel Pat Cipollone. “I think it is appropriate at this point for me to admonish both the House managers and president’s counsel in equal terms to remember that they are addressing the world’s greatest deliberative body,” he said last Wednesday night. At once, Justice Roberts signaled to the Senate and the world that he might not sit as a “potted plant,” little more than a master of ceremonies. But how much of a role will Chief Justice Roberts play in the next phase of the proceedings?

The Constitution defines impeachment trial roles for the Senate and Chief Justice in Article I, Section 3. “The Senate shall have the sole power to try all impeachments… When the President of the United States is tried, the Chief Justice shall preside.” What exactly does it mean for the Chief Justice to “Preside” while the Senate has “sole power” to try the case? In the trial of President Bill Clinton, Chief Justice William Rehnquist let the Senate Majority and Minority Leaders work out procedural matters with little or no guidance. “I did nothing in particular, and I did it very well,” Rehnquist quipped. This was made easier because Senate Majority Leader Trent Lott and Minority Leader Tom Daschle had agreed on key matters of procedure.

Many commentators have assumed that Roberts would follow in the Rehnquist vein, “calling balls and strikes” as Roberts put it in his confirmation hearing. He would merely keep the process moving along without offering his own commentary or direction on important procedural matters.  It is certainly possible that he will continue to do so. After all, Roberts’s warning to the House Manager and White House Counsel was little more than a plea for both sides to cool off and lower the temperature a bit to preserve the decorum fitting such a solemn proceeding. Brenda Wineapple, author of a superb new book on the Andrew Johnson impeachment, predicted before the trial began that Roberts would be “extremely cautious” about delving into any partisan divide because “that flies in the face of the myth that the court is above partisan politics.” Roberts’s brief remarks might be more than Rehnquist ever uttered, but they hardly amount to a substantial intervention in the case.

But one thing already sets the Trump case apart. Unlike the comity present between Lott and Daschle, Senate Majority Leader Mitch McConnell and Minority Leader Chuck Schumer are clearly at loggerheads over critical procedural matters, especially the calling of witnesses. Up to now, the Senate has performed its “sole power” by holding majority votes to begin the trial without a commitment to hear witnesses, the votes falling along partisan lines, 53-47. Should every future procedural vote also fall along partisan lines, Chief Justice Roberts may end up doing just as little as Rehnquist did.

However, there are at least two scenarios where Roberts may be called upon to wade into a trial already marked by deep partisan rancor and mutual suspicion. First, if a vote on witnesses or acceptance of claims of executive privilege (or any matter) results in a 50-50 tie, the Chief Justice – and not the Vice President – will be forced to cast a tiebreaking vote. Roberts would then have no choice but to rule on substantive matters that he undoubtedly wants to avoid. Second, the question of whether to issue subpoenas to witnesses might come to Roberts’ directly under the Senate’s Standing Rules on impeachment (see Neal Katyal, Joshua Geltzer, and Mickey Edwards’ analysis). For guidance on how to navigate in his role on these matters, Roberts can look not to the taciturn Rehnquist but to another precedent: Chief Justice Salmon P. Chase and his more active management of the impeachment trial of President Andrew Johnson.

The Ambition of Chief Justice Chase

Salmon Chase took a very different road to the high court than did Roberts, who served in the Solicitor General office, at a corporate law firm, and on the US Court of Appeals for the DC Circuit. Chase had been an activist and politician for decades before rising to the Court. As a lawyer, Chase defended fugitive slaves in Ohio and helped found the Free Soil Party and later the Republican Party. First elected US Senator in Ohio, Chase later served as Governor leading up to the Civil War. Ever ambitious, Chase sought the Presidential nomination in 1860, gaining 49 votes from Ohio on the first ballot at the Chicago convention of the Republican Party. He pledged his loyalty to Lincoln after the convention and subsequently earned appointment as Secretary of the Treasury in 1861. Chase ably managed the nation’s finances during the Civil War, cautiously issuing greenback currency and avoiding hyper-inflation while funding the Union war effort. In 1864 Lincoln feared Chase would run again for President with support from the more radical elements of the Republican Party. Partly to forestall that, Lincoln appointed Chase to the Supreme Court upon the death of Chief Justice Roger B. Taney.

Once appointed and confirmed (in a single day), Chase worked hard to strengthen the Supreme Court’s authority, no small task for an institution long defined by the odious Taney.  Reconstruction Constitutional Amendments fundamentally altered the relationship between the federal and state governments. As Allen Guelzo argues in his recent study of Reconstruction, Chase eagerly defended the new federal powers over matters of civil and voting rights for African Americans. At the same time, Chase insisted that federal courts should only intervene when state authorities explicitly violated freed people’s civil rights and state courts denied avenues for redress. Chase’s rulings also re-established the primacy of civilian courts once the war ended (Ex Parte Milligan) and asserted the power of the judiciary in declaring secession unconstitutional in the Texas v. White decision in 1868. Ever the ambitious pol, however, Chase continued to wade into politics (even though his partisan allegiances shifted in 1870) and he openly backed opponents of President Grant.

Presiding Over the Johnson Impeachment Trial

The impeachment and trial of President Andrew Johnson in 1868 provided the ultimate platform through which Chase could place his stamp on the Judiciary, and on American law generally. Johnson’s impeachment for violation of the 1867 Tenure of Office Act unified most Republicans, who comprised a super-majority in both houses of Congress. Loathed by most Republicans for his obstinate refusal to defend the rights of freed people, Johnson found himself facing near-certain removal when he fired Secretary of War Edwin Stanton without seeking Senate approval as the Tenure of Office Act required. That Act had been passed precisely to preserve Congress’s power over Reconstruction so it was no mere technicality, even though the Act would later be found unconstitutional.

House Managers faced three challenges on the road to conviction. First, it was unclear if the Tenure of Office Act applied to Stanton since he had been appointed by President Lincoln and not Johnson. Chase was among those who felt that the Tenure of Office Act did not protect Stanton and so he personally supported acquittal. Moreover, he was sympathetic to the Johnson defense argument that the President was merely setting up a test case on the Tenure of Office Act’s constitutionality and not acting with malicious intent to abuse his power. Second, with the Vice Presidency vacant at the time, the law of succession would elevate Senate Pro Tempore Benjamin Wade to the Presidency in the event of Johnson’s conviction. Wade and Chase were fellow Ohio Republicans, equally ambitious and jealous of the other’s careers, and they held very different views on economic matters like the protective tariff. Chase (like many other Senators) had no desire to see Wade become President. A third factor was a growing rift within the Republican Party itself, with Radicals pushing more incessantly for conviction and Wade’s elevation to the White House, and moderate conservatives who hoped a unifying figure like Ulysses Grant could become President in the November 1868 elections. Whatever misgivings Chase had about Grant’s nomination to the Republican ticket, they paled in comparison to his hatred of Wade.

Hardly impartial, then, Chase put his stamp on the impeachment trial proceedings right away. Senators debated the role for the Chief Justice to play, with some hoping to grant him full authority to rule on “all questions of law and evidence” (Benedict, p. 116) while others wanted to curtail his authority entirely. The Senate agreed to a compromise measure that allowed the Chief Justice to ‘submit to the Senate, without a division, all questions of evidence and incidental questions; but the same on demand of one fifth of the members present, shall be decided by yeas and nays.” (Congressional Globe, March 2, 1868, Senate Journal, Appendix, p. 795) This ambiguous proposal opened the door for Chase to assert his role by insisting the Senate had effectively become a court and that he could cast a tie-breaking vote as a fellow member of that court. Had the Senate not agreed to Chase’s seemingly rhetorical point about the Senate-as-court, Senators could have declared that Chase, not being a Senator himself, could offer no substantive ruling on matters of law and procedure.

Chief Justice Chase and witnesses

Much like the contentious votes on witnesses at the start of the Trump trial, the Johnson trial “court” held a series of key votes on procedural issues, the most important of which had to do with timing and witness relevance. Radicals who demanded Johnson’s conviction wanted a quick trial to capitalize on public outrage over Johnson’s recent violation of the Tenure of Office Act. Conservatives argued that the trial should proceed more deliberatively and managed to force a 25-25 tie on the question. Chief Justice Chase broke the tie and voted in favor of the lengthier trial, which proved crucial in helping the defense rally support for the President. Chase cast similar tiebreaking votes on the admissibility of certain witnesses whom the White House Counsel called to testify to the fact that Johnson was merely challenging the constitutionality of the Tenure of Office Act and not violating the law as an abuse of Presidential power.

But Chase also issued rulings on the admission of witnesses and evidence that were not about breaking ties, but simply the umpire-like management that one expects with a judge presiding over a case. In those instances, the Senate sustained him. For example, in one instance, an objection was made that a line of new questions posed to General William T. Sherman would be tantamount to calling him back as a witness. Chase was not shy to make the call. “The Chief Justice thinks it is entirely competent for the Senate to recall any witness,” he said. Later in the trial when President Johnson wished to introduce statements he made after House impeachment proceedings started that he honestly did not believe Stanton was covered by the Tenure of Office Act, Chase ruled against the Defense. Chase rejected that evidence because, at this point in time, the accused were generally not allowed to testify at all in criminal procedures.

In the end, the Senate voted to acquit Johnson by one vote. The reasoning of the seven Republican “recusants” was that they believed Johnson innocent of the charge that he violated the Tenure of Office Act. Chase did not have a vote on the final acquittal and never insisted upon one. In the end he was judge but not juror. But his procedural intervention helped prolong the trial and grant the defense the right to call certain witnesses.

In Chief Justice Roberts’ court

Justice Roberts shares none of the ambitions of Justice Chase. In fact, his depiction of the Court’s role as “calling balls and strikes” cast him outside partisan politics, as Wineapple notes. Ruth Marcus correctly warns against looking to the biased Chase as an example of ruling out certain testimony as irrelevant. And yet, Roberts may find he has no choice but to intervene in the proceedings of the Senate-as-court, for instance, if a vote to call witnesses results in a 50-50 tie. If three Republican Senators – no more and no less – vote to hear witnesses, Roberts will be called upon to approach the Senate-as-court as a trial judge would. How would Roberts rule then? The GOP argument is that the Senate is under no obligation to hear witnesses that the House did not call. As Roberts surely knows, this is rather self-serving considering the refusal of the White House to allow Administration officials to testify. More importantly, the fact that the House impeachment is akin to a Grand Jury indictment and not a trial court, Roberts knows that no trial judge would ever claim that Prosecutors cannot call witnesses that were not called in Grand Jury proceedings. An impeachment trial is not a criminal trial, of course. But in many ways it is “like” a criminal trial with Roberts playing the role of trial judge. If Chief Justice Roberts is thrust into the position of trial judge, and the Senate vote on witnesses results in a 50-50 tie, it is hard to imagine he would refuse to hear witnesses. To do so would mean he was advancing exactly the sort of partisan Senatorial argument that he hopes to avoid.