He was often called the dean or the soul of the Senate, but to many of his colleagues, the late Sen. Robert Byrd was the man who taught them how to be a Senator.

Following the death early Monday of the longest-serving Member in history, Senators reflected on the end of an era in which the West Virginia Democrat figured prominently in their own careers — and many came up empty when asked who would fulfill that role for future generations of Senators.

“Robert C. Byrd became known as the soul of the Senate, a fierce defender of the Constitution, respected historian, and an absolutely fearless legislator,” Sen. Jay Rockefeller (D-W.Va.) said. “He literally wrote the authoritative procedures of the Senate, taught all of us about that in classes which he would conduct. … I think he leaves a void that probably cannot be filled.”

Senate aides struggled to name another Senator who would or could take on a similar role for incoming Members particularly given the nearly impossible task of filling Byrd’s shoes. The 92-year-old was third in line to the presidency by virtue of his position as President Pro Tem, while he also held nearly every Senate leadership role, including Majority Leader from 1977 to 1981 and from 1987 to 1989.

Byrd died Monday after a short stint at Inova Fairfax hospital. He was admitted for dehydration and exhaustion last week, but his office announced he was “seriously ill” on Sunday.

Senate Historian Don Ritchie once said Byrd was more like his 19th-century counterparts than his 20th-century contemporaries. After all, he served for a total 56 years in the House and Senate. He wrote a four-volume, authoritative history of the Senate. And he was a man who believed it was his Senatorial duty to give speeches filled with poetry as well as those addressing what many might consider mundane or trivial events. For example, up until his health failed, he was on the Senate floor at the advent of every major holiday to laud its virtues, and he often gave speeches praising the changing of the seasons.

“It was appointment viewing for Senators and staff alike,” said one senior Senate Democratic aide, who noted that while sometimes the sentiments might seem quaint, “His passionate earnestness overcame you.”

It was that passion for the Senate and its rules that endeared him to his colleagues and engendered the deep reverence Members still feel for him.

Of course, Byrd was not the first to mentor new Members as they entered the chamber, but he appears to have been one of the most enduring.

Byrd assumed the role of “father” of the Senate in the late 1970s, according to the Senate Historical Office. From the 1970s until 1998, he spoke regularly on the history of the Senate at freshman orientation meetings, the historian’s office said. He continued to advise new Senators intermittently since then.

Sen. Chris Dodd, who served with Byrd for 30 years and sat next to him on the Senate floor for 25 years, said he remembers well when Byrd presented him with a copy of the U.S. Constitution, which Byrd also constantly carried in his breast pocket.

“I’ve carried this with me every day of my life for the last quarter of a century,” said the Connecticut Democrat, who noted it was “given to me by my colleague in this chamber along, I might add, with a stern but kind lecture on Senate protocol.”

Even the man who succeeded Byrd as both Appropriations chairman and President Pro Tem, Sen. Daniel Inouye, credited Byrd with helping to shape his own 47-year career.

[IMGCAP(1)]”Nearly 48 years ago Senator Byrd was one of the first to greet me in the chamber of the United States Senate,” the Hawaii Democrat said in a statement. “He was my mentor. Over the years he provided me countless opportunities and tasked me with positions of critical national oversight while guiding my actions with the temperance he learned as the longest serving Senator in history.”

In a 2006 speech, Sen. Patty Murray (D-Wash.) said she remembered the day Byrd schooled her and other class of 1992 freshmen on how to preside over the Senate.

“Sen. Byrd, at the time, brought in all of us freshman Senators to sit across from him in his very important office and looked down at us and told us that we would be presiding, as is the presiding officer today, and told us about our responsibilities and made it very clear he would be watching from his office, and if we were reading any other material or talking to anyone it would be noted,” she said.

Members from both sides of the aisle turned to Byrd for advice and mentorship, and aides said unlikely bedfellows such as Sens. Tom Coburn (R-Okla.) and former Sen. Norm Coleman (R-Minn.) often sought him out on the Senate floor. But that uniquely nonpartisan coalition of appropriators perhaps knew him best.

Former Sen. Ted Stevens (R-Alaska), who served as both Appropriations chairman and ranking member with Byrd, said he “was one of the greatest orators of the Senate” and a master of history whose acumen was on full display when the two participated in the parliamentary conferences with the British Parliament.

“I will never forget one evening when a guest from Great Britain made an ‘off the cuff’ remark that ‘Americans know little about the history of the British monarchy,'” Stevens recalled in a statement. “Senator Byrd, in his unpretentious gentlemanly remarks, proceeded to name every monarch in Britain’s history, including the Queens, Consorts, legitimate and illegitimate pretenders, from memory.”

Byrd’s involvement mentoring freshman Members waned in recent years as his health declined, and his lack of influence over the more bullish 2008 class seems apparent in their rebellious push to reform Senate rules, particularly the rule that requires 60 votes to shut down an attempted filibuster. In the past, even a whisper of a radical rules change, such as doing away with the filibuster, would have earned a swift response from Byrd, as it did when Republicans attempted in 2005 to eliminate filibusters of judicial nominees.

Byrd made a point of appearing at a Rules and Administration Committee hearing last month on the issue of filibuster reform. Byrd delivered a nearly 15-minute address to a hushed room eager to listen to the maestro’s procedural instructions. During that May 19 hearing, Byrd cautioned against any radical reforms of the filibuster but offered a suggestion for potential compromise.

“Over the years, I have proposed a variety of improvements to Senate rules to achieve a more sensible balance allowing the majority to function while still protecting minority rights,” Byrd said at the hearing. “For example, I have supported eliminating debate on the motion to proceed to a matter [except for changes to Senate rules] or limiting debate to a reasonable time on such motions, with Senators retaining the right to unlimited debate on the matter once before the Senate.”

Rules and Administration Chairman Charles Schumer (D-N.Y.) called it “a hallowed moment.”

The filibuster reform debate, nuanced and academic, was tailor-made to be Byrd’s curtain closer. It was anchored by two other top Byrd priorities — the April mining disaster in West Virginia and a push by President Barack Obama for line-item veto power — that briefly drove the news cycle and allowed the Democrat an opportunity to re-emerge.

Lashing out over Obama’s line-item veto proposal, Byrd reminded: “Congress has the constitutional authority over the power of the purse, and I am not in favor of yet another attempt at a power grab by a chief executive.”

Given the respect Byrd enjoyed from Majority Leader Harry Reid (D-Nev.) and the entire Democratic leadership structure, it was difficult in 2008 for leaders to consider replacing Byrd atop the powerful Appropriations Committee. Aides said care was taken to make sure Byrd did not feel pushed out but that leaders needed him to realize on his own that he was too frail to continue as chairman.

Byrd was forced to use a wheelchair for the past several years, and he spent several weeks in the hospital in May and June of last year. He was rushed by ambulance to a hospital Sept. 22 after falling at his Northern Virginia home.

But few were remembering Byrd’s decline on Monday.

Senate Majority Whip Dick Durbin (D-Ill.) said he got a lesson in Byrd’s influence in 2002, when both men were opposing the Bush administration’s efforts to go to war in Iraq.

“My wife and I went to a Mass at Old St. Patrick’s Church in Chicago, and after the Mass, we were in the pews, kneeling down after communion, and the church was quiet as people were returning from communion, and an older fellow whom I didn’t know stood next to me in the aisle and looked down at me and in a voice that could be heard across the church, he said, ‘Stick with Bob Byrd,'” Durbin said on the floor Monday. “I came back and told [Byrd] that story and he just howled in laughter.”