OTTAWA -- Montreal's mayor, Gérald Tremblay, resigned Monday evening in the midst of an eyebrow-raising inquiry that has revealed widespread corruption among city officials, contractors and members of organized crime.
The hearings have not demonstrated that Mr. Tremblay, who has been mayor of Montreal, Canada's second-largest city, since 2001, directly benefited from the corruption. But one former mayoral aide, who was later a policy adviser to Prime Minister Stephen Harper, testified that Mr. Tremblay knowingly turned a blind eye to illegal fund-raising activities by his Union Montréal political party. Its efforts that were so successful, the aide said, that the party's safe became so overstuffed with $100 and $1,000 bills that its door would not close.
While rumors about corruption have surrounded Mr. Tremblay and several other politicians in Quebec for years, testimony at the public inquiry, commonly known as the Charbonneau Commission for its president, Justice France Charbonneau, suggested that its extent may be far greater than imagined. The testimony has also provided a glimpse into the mechanics of Quebec-style corruption.
Mr. Tremblay is the first politician to resign because of the inquiry, which is far from over. But some observers suggest that it was the issue of corruption that fueled the widespread student protests earlier this year and that the issue also led to the defeat of the Liberal provincial government, which had reluctantly assigned Ms. Charbonneau to examine the problem.
In May, a special anticorruption police squad arrested Frank Zampino, who was once Mr. Tremblay's closest political ally at City Hall, and charged him with fraud, conspiracy and breach of trust related to a $300 million municipal contract.
But when Mr. Tremblay announced his resignation in Montreal's City Hall -- a building whose roof repair was the subject of earlier corruption allegations -- he remained defiant and insisted that he was a leader of the anticorruption movement.
Mr. Tremblay insisted that he was not aware of what was going on around him until late in the last decade, and he denied that he was deliberately looking away from wrongdoing by his party. His resignation, he said, was intended to end the political gridlock the corruption allegations had brought to the city's politics.
"Under these circumstances, I cannot help anymore," the usually avuncular but now somber leader said. "The success of our city is much more important than my personal interest."
Martin Dumont, a former political organizer, testified that when the subject of illegal campaign donations came up at a 2004 meeting, Mr. Tremblay said, "I don't want to know about that," and abruptly left. On Monday, however, the mayor said that no such episode took place and added, "I am going through a period of unbearable injustice."
Mr. Dumont stood out from several of the other witnesses heard by the inquiry to date because he was not on the take.
Gilles Suprenant, a retired city engineer, had trouble recalling exactly how much cash he received from contractors. Still, he appeared at the hearing with a plastic bag containing $122,800 in kickback money. He said that he gambled away about $250,000 of dirty money at Montreal's government-owned casino, which he characterized as a way of paying back taxpayers.
Although he described himself as a "simple bureaucrat," Mr. Suprenant estimated that he received more than $700,000, plus a large number of free meals, hockey tickets and vacations, for allowing contractors to inflate prices on city contracts. A former colleague testified that his first payoff came in the form of a Christmas card from a contractor that contained a $1,000 bill.
Police testimony at the inquiry has indicated that the contractors were also paying off organized crime figures. The commission saw a surveillance video of Niccolo Rizzuto, who the police say was an organized crime leader and who was later killed in his home by a sniper, receiving cash from contractors in a now-defunct Italian social club and stuffing it into his socks.
Denis St. Martin, a political scientist at the University of Montreal, said that political corruption has festered in Montreal for decades and has been protected by a relatively closed political system.
But he said an increase in the level of corruption in recent years has contributed to election upsets in Quebec, undermined the government's ability to deal with disruptive student protests and finally forced the inquiry.
"The old bargain has eroded so we are now at the point of rupture," Mr. St. Martin said. "We now see the politics of Montreal shifting in a very rapid way."
Correction: November 6, 2012, Tuesday
This article has been revised to reflect the following correction: An earlier version of this article referred incorrectly on second reference to Justice France Charbonneau. Justice Charbonneau is a woman.
This article originally appeared in The New York Times.