This story originally ran on September 29, 2019. It has been updated with details of the current House impeachment effort.

Washington (CNN) Two decades ago, Chief Justice William Rehnquist captured unprecedented attention as he presided over the Senate trial of a president, a role that would fall to Chief Justice John Roberts if the US House were to impeach President Donald Trump and a Senate trial were launched.

Finding the chief justice in such a public setting offered a sea change from his usual place in the secretive third branch of government. Cameras are barred from Supreme Court proceedings and the justices, when they do speak publicly, are cagey about internal deliberations or disagreements.

As Rehnquist told senators back in 1999: "I underwent the sort of culture shock that naturally occurs when one moves from the very structured environment of the Supreme Court to what I shall call, for want of a better phrase, the more freeform environment of the Senate."

Rehnquist's correspondence from 1998 and 1999, contained in his archive at the Hoover Institution at Stanford University, reveals some of the dilemmas the chief justice weighed at the time and the attention he drew.

His concerns ranged from the intricacies of Senate rules to whether he could obtain a tax deduction for donating his black robe, famously bedecked with gold stripes on the sleeves, to the Smithsonian.

For Rehnquist, the experience of sitting on the dais above the senators' wooden desks was inspiring. "[I]t is an historical occasion, and it has given me a chance to see the Senate in action at first hand," he wrote to a friend in January 1999 as the five-week trial of President Bill Clinton was underway.

Rehnquist, who died in 2005 and was succeeded by Roberts, was an amateur historian who in 1992 had written a book about impeachment. He understood the weight of the moment but also that the leading players in it were senators. He saw his role as largely ministerial and relied heavily on a Senate parliamentarian.

"On several occasions when asked what I did at the trial," Rehnquist wrote to a man in Carson City, Nevada, "I took a leaf out of [the Gilbert and Sullivan comic opera] Iolanthe and replied, 'I did nothing in particular, and did it very well.'" The gold stripes that Rehnquist had affixed to his robe years earlier also had been inspired by a character in Iolanthe.

Yet Rehnquist also groaned that he still had to keep up with the usual run of Supreme Court cases, so, as he wrote in one letter, "the trial is in one sense an unwelcome burden ... I have been relieved of none of my responsibilities here at the Court."

The magnitude of an impeachment trial for a US president -- only two have been held in US history -- is underscored by the Constitution's specific mention that the chief justice presides.

The House Intelligence Committee held several public hearings in November with witnesses in its impeachment inquiry. The House inquiry is focused on Trump's effort to persuade Ukrainian President Volodymyr Zelensky to investigate former Vice President Joe Biden, a possible Democratic rival to Trump's reelection bid, and his son, Hunter.

House Democrats are working on articles of impeachment and a formal vote could come in December.

If the House were to vote to impeach Trump, it would fall to the Senate to decide whether to convict or acquit, with Chief Justice Roberts presiding. That could create some angst for Roberts, who has increasingly tried to separate the court from the political polarization seizing the country.

Suddenly in the spotlight

The then-Republican-controlled House of Representatives had impeached Democrat Clinton in December 1998, partly based on his grand jury denial of a sexual relationship with former White House intern Monica Lewinsky.

Clinton's Senate trial, which began on January 7 and ended February 12, 1999, was only the second such hearing in US history. President Andrew Johnson's 1868 trial was the first, and he -- like Clinton -- was acquitted. A vote of two-thirds of the Senate is required for conviction; to impeach in the House, only a simple majority is needed.

Under Senate rules, Rehnquist's specific impeachment files are closed to the public along with other Senate trial materials. But his private correspondence from the months that he handled related issues is available in his Hoover Institution papers.

Before the trial, Rehnquist was not a familiar public face, despite having been a justice since 1972 (appointed by Richard Nixon) and chief since 1986 (elevated by Ronald Reagan). But when Rehnquist began presiding at the nationally televised Senate trial, he heard from old school chums, former colleagues, and regular citizens captivated by the trial.

Many people wrote about his bad back. Rehnquist would stand periodically during the trial to stretch, as was his practice during Supreme Court oral arguments. A woman from Mobile, Alabama, sent him a Sacro Wedgy back support device, and a man from Independence, Missouri, promised a chinning bar.

Rehnquist, then 74, responded to the latter: "The chinning bar will join at least a dozen other devices and remedies which other back sufferers have sent to me since the impeachment trial began."

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The chief justice also became grist for humorists such as Dave Barry and late-night comics such as David Letterman, particularly for those untraditional gold stripes. Yet senators and legal analysts praised Rehnquist for an even-handed approach. His first ruling drew notice for going against Republican House managers who were presenting the case for a Clinton conviction.

In that instance, Rehnquist upheld an objection of Democratic Iowa Sen. Tom Harkin to the House managers' referring to senators as "jurors." Declared Rehnquist, "The Senate is not simply a jury. It is a court in this case."

In a separate episode documented in Rehnquist's personal correspondence, Harkin sent a letter to Rehnquist asking him to adopt certain limits on the House managers' questioning of potential witnesses. Rehnquist begged off.

Referring to Senate rules for trial of impeachments, Rehnquist wrote on January 25, "I am by no means certain that I might issue the sort of order you request when the Senate is out of session. But assuming that I have such authority, I would want to use it only ... (when) clearly warranted."

Harry F. Byrd Jr., who had been a US senator from Virginia, told Rehnquist in a note that senators usually do not like listening to fellow senators, and like listening to House members even less. Rehnquist responded, "How true!"

When a friend from Rehnquist's early law-clerk days at the court grumbled about the public fascination with Lewinsky, after she had been interviewed by ABC's Barbara Walters in early March, Rehnquist wrote, "I couldn't bring myself to read or watch any of the 'Monica' interviews -- what a sad commentary on the country that 69 million people would watch the television presentation!"

What Rehnquist may have thought of Clinton does not emerge in his correspondence. But his file does include a birthday greeting from the White House, sent on September 29, 1998, two days before Rehnquist's October 1 birthday and just as the impeachment possibility was heating up.

The note does not appear to be especially personal. It is addressed simply to "Justice Rehnquist," and says, "Happy Birthday! Hillary and I want to wish you the very best on this special occasion and a happy, healthy year to come."

Early preparations

In September 1998, Independent Counsel Ken Starr had submitted his report extensively detailing Clinton's relationship with Lewinsky and listing grounds for possible House impeachment.

That September Rehnquist also heard from people asking to assist him if a trial were held. Washington lawyer Neal Katyal, a former Supreme Court law clerk, wrote on September 15, 1998: "In the event that you are interested in hiring a part or full-time law clerk to assist you with any matters related to impeachment, I would be honored to work for you."

"As you might expect," Rehnquist responded on September 30, 1998, "I expect to cross that bridge only when I come to it. I will keep your letter on file." Katyal, who said recently he does not recall the correspondence, today is a regular appellate advocate before the Supreme Court and a prominent critic of Trump.

As Rehnquist wrapped up his work with the Senate, he was in contact with the Smithsonian Institution about the robe he wore for the historic event.

"I will certainly consider donating to the Smithsonian the robe I wore during the Senate impeachment trial," Rehnquist told the secretary of the Smithsonian in March. "If you want it now, please let me know how I can either get a tax deduction or a new robe at someone else's expense."

Rehnquist apparently received what he needed for a tax deduction. A year later, the chief justice recorded that he had donated the robe to the Smithsonian, according to an Associated Press 2000 report on the justices' annual financial disclosure forms.

Sotheby's, the chief justice noted, had appraised the robe at $30,000.