"When you live in a polarized political environment, people tend to see everything in those terms," Roberts said in September. "That’s not how we at the court function and the results in our cases do not suggest otherwise."
Now, with a Senate trial of the president possibly set to launch next month – depending on if and when House Speaker Nancy Pelosi transmits the articles – the man at the center of the highest court, both ideologically and figuratively, is poised to preside over proceedings.
The unique assignment is dictated by the Constitution. With Roberts at the helm, it would mark one of the few times the highest levels of the three branches collide in a political fight – one that may last only weeks, but whose effects can ripple for decades.
And given simmering tensions between Trump and Roberts, the chief justice's conduct in this role would be closely watched by both parties.
Sources say Roberts will be ready, having quietly reached out to associates in recent weeks over the role he would play in managing the trial. He may rely on the Rehnquist Model: how former Chief Justice William Rehnquist deftly handled the 1999 impeachment trial of President Clinton.
"Chief Justice Rehnquist did bring a sort of solemnity to the occasion or a seriousness that tried to sort of tamp down maybe on politics and really focus on the facts of the case," said Robert Schaffer, who was a Rehnquist law clerk during that momentous court term.
Despite voting as a member of the high court a year earlier to allow a sexual harassment lawsuit against Clinton to proceed -- which set the subsequent impeachment process in motion -- there was no real objection to having Rehnquist preside. The Paula Jones case led to Clinton being tried over perjury and obstruction of justice, for his later statements made under oath where he denied an affair with White House intern Monica Lewinsky.
But like the Clinton proceedings, the script of the Trump trial may already be set before Roberts ever gavels the spectacle to order.
Senate leaders -- both Republicans and Democrats -- are working to finalize the trial length, testimony and exact role of the president's counsel. And it will be lawmakers -- the "jury," in effect -- who would establish the exact rules of trial, not the judge.
"[Rehnquist] was content to allow the Senate to control its own procedures," said Schaffer. "And really, he viewed himself as a guest of the Senate during the impeachment trial."
But that does not mean Roberts would be marginalized. Rehnquist issued important rulings guiding senators on impeachment procedures.
And he spoke from experience, writing a 1992 history book on the 1868 impeachment of Andrew Johnson, "Grand Inquests."
"The importance of the acquittal [of President Andrew Johnson] can hardly be overstated," Rehnquist wrote, something Trump today might approve. "With respect to the Chief Executive, it has meant that as to the policies he sought to pursue, he would be answerable only to the country as a whole in the quadrennial Presidential elections, and not to Congress through the process of impeachment.”
When it was done, Rehnquist described his role, by using a line from a favorite Gilbert and Sullivan operetta, "I did nothing in particular, and I did it very well."
Now Roberts, who was once a law clerk to Rehnquist, gets his turn at history.
A hybrid between a courtroom trial and a legislative debate, Senate impeachment trials mix ceremony and substance.
The chief justice of the United States would be sworn in first, then the senators. He would wear his judicial robes at every public session, from the seat normally reserved for the presiding officer. And he would be tasked with maintaining order with the chamber's traditional handle-less ivory gavel.
Roberts' main role would be to make any rulings on procedure raised by senators, the House impeachment managers or the president's counsel. But while he could decide on evidentiary questions or objections, the chief could choose to have senators instead vote on those matters. Or the lawmakers could override any Roberts rulings with a majority vote.
And since the senators are not allowed to speak, any questions they submit in writing would be read aloud by the judge.
The chief's main power may be in breaking any tie votes. Chief Justice Salmon P. Chase made two such votes during the Johnson trial.
Roberts would also be multi-tasking, conducting a trial at the same time maintaining his regular caseload. The court's counselor Jeffrey Minear would likely be by the chief's side the entire time, along with a rotating pair of law clerks.
When in the Capitol, they will all likely work from the ceremonial President's Room, located just off the Senate floor.
"We continued to do all the work of the court," said Schaffer of his experiences. "So there were times when we would bring opinions over to the to the Senate for the chief justice to read, to review and to vote on."
Face of Justice
As the "face" of the third branch, Roberts has been a stout defender of the 870 active federal judges, knowing that many of the public views them as "politicians in robes."
The "chief," as he is informally known around the court, has publicly stated his long-term efforts to forge consensus with his colleagues whenever possible, show respect for precedent and preserve the court's reputation.
"If we uphold a particular political decision, that remains the decision of the political branches, and the fact that it may lead to criticism of us is often a mistake," he said in 2016. "We do have to be above or apart from the criticism because we, of course, make unpopular decisions -- very unpopular decisions."
But Trump has been more blunt, taking a results-oriented consistency when judging the judges.
In particular, Roberts' dramatic 2012 deciding vote upholding the key funding provision of the Affordable Care Act triggered conservative criticism that it was a calculated act of betrayal, a narrative Trump was all too eager to exploit on the campaign trail.
"Justice Roberts really let us down," Trump said at a campaign rally in December 2015. "What he did with ObamaCare was disgraceful, and I think he did that because he wanted to be popular inside the Beltway."
In a rare public rebuke, Roberts responded a year ago when Trump criticized a legal setback over his immigration policy as the work of an "Obama judge."
The chief justice responded, "We do not have Obama judges or Trump judges, Bush judges or Clinton judges. What we have is an extraordinary group of dedicated judges doing their level best to do equal right to those appearing before them."
Roberts has voted with his more liberal colleagues to put some of the president's policies on hold. And just weeks after any Senate trial, he would preside over oral arguments concerning Trump's refusal to turn over his banking and financial records, in the face of subpoenas from House committees and a state grand jury.
It comes as the public still holds the Supreme Court in high regard. A Fox News Poll from early October found 68 percent of those surveyed have confidence in the institution, far greater than the president or Congress. But just two years ago, confidence in the Supreme Court was 83 percent.
The chief justice, for the most part, has maintained his steady, low-key leadership under both Republican and Democratic presidents, and the 64-year-old Roberts is unlikely to care much what is said about him personally. Life tenure on the bench gives him such security.
But he knows maintaining his -- and the court's reputation -- during a hyper-partisan impeachment drama will test his leadership skills. Colleagues say he is fully prepared for the challenge.
"He has a history of being a very impartial, fair, almost umpire-like justice, who calls them as he sees them," said Schaffer. "I don't think he'll treat this trial any differently."
Fox News’ David Spunt contributed to this report.