Nolin, 64, who was appointed to the Senate by Brian Mulroney in 1993, died just after 7 p.m. Thursday, not long after the upper chamber issued a statement warning that his health had recently taken an abrupt turn.
Mulroney said Nolin "played a large part" as one of his chief organizers in his 1983 leadership campaign and the Conservative election campaigns of 1984 and 1988.
"He was a very entertaining and warm and friendly guy," Mulroney said in an interview.
"Even after his illness he retained his sense of humour, and his sense of optimism about life and about Canada. He was a delightful guy ... proud to have had him as a friend."
Nolin became Speaker just last November, the unanimous choice of Conservative, Liberal and independent senators who saw him as a smart, respected, open-minded man who could steer the upper chamber through the final dramatic chapters of the expenses scandal that has rocked the Senate to its foundations.
His death comes in the midst of the trial of suspended senator Mike Duffy for allegedly filing fraudulent living and travel expense claims. The trials of two other senators, Patrick Brazeau and Mac Harb, on similar charges are set to start within months and the RCMP continue to investigate a fourth, Pamela Wallin.
The auditor general, meanwhile, is finishing up an unprecedented audit of all senators' expenses and is expected to report his findings in June.
Prime Minister Stephen Harper said Nolin served in the Senate "with great devotion" for 21 years, noting his interest in causes like human rights, the Canadian military and the place of Quebecers in a united Canada.
"He worked very hard," Harper said during an event in Winnipeg.
"He was very devoted, and was particularly so during these last few years while he was fighting cancer. We all admired him for that, just doggedly pursuing his duties."
In an earlier statement, Harper described Nolin as "part of that small group of persons whose life and example have enhanced the institution they served while contributing to the common good."
The Queen expressed her "great sadness" at Nolin's passing. Governor General David Johnston acknowledged his "character, independence of mind and integrity."
Even NDP Leader Tom Mulcair, a champion of Senate abolition who rarely has a nice word for the institution, paid tribute, calling Nolin "a real gentleman who dedicated his career to public life and served Parliament and the public with competence and devotion."
When he took over the Speaker's chair, Nolin signalled his intention conduct himself in a non-partisan manner and to devote himself to defending and restoring the reputation of the tarnished upper house.
As Speaker, Nolin was also chair of the Senate's internal economy committee, which establishes the rules for how senators can spend taxpayers' dollars and claim reimbursement for expenses.
In his last public comments earlier this week, Nolin vowed to tighten those rules and make senators more accountable.
"Under my leadership as Speaker, the Senate is committed to modernizing its rules and processes in keeping with best practice standards," Nolin said in a statement issued Monday to The Canadian Press.
Although he was a loyal Conservative, Nolin had an independent streak. He voted against his party on a number of occasions and spoke out against Harper's doomed initiative to turn the appointed upper house into an elected chamber.
Nolin also bucked the Tory tide in 2002 when he chaired a special Senate committee that recommended legalizing marijuana.
Claude Carignan, the government leader in the Senate, called "P.C.," as Nolin was known to friends and colleagues, an inspiration and a mentor and said his death is a "great loss."
"While Pierre Claude was a member of our Conservative family, he was respected on both sides of the aisle because of his fierce independence," Carignan said.
"He will be remembered by each and every one of his Senate colleagues for his integrity, knowledge, wisdom and determination."
James Cowan, leader of the Senate Liberals, said Nolin was "admired and respected by all who knew him" and his ascendency to the Speaker's chair "universally applauded."
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