Mayor Michael Applebaum, who took the reins at Montreal city hall on a promise to tackle corruption and restore public trust, now faces a battery of corruption-related charges himself, and a chorus of calls from the Quebec Premier and others to resign.

Mr. Applebaum was arrested at his home early Monday morning, leaving Montrealers' confidence further shaken and raising vexing questions about political leadership in Canada's biggest cities.

In a little more than half a year, Montreal mayor Gérald Tremblay resigned after allegations about illegal fundraising, and now his replacement is facing replacement.

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Only last fall, Mr. Applebaum was portraying himself as a reforming white knight promising to tackle the corruption that has cost taxpayers millions and sapped the trust of a cynical electorate. "I solemnly vow that I will erase this stain on our city," he said as he became interim mayor of Canada's second-largest city, taking over from Mr. Tremblay.

Today, the crusader finds himself under the weight of criminal charges. Mr. Applebaum is charged with 14 criminal counts, including conspiracy, fraud and breach of trust.

He was released from provincial police headquarters after more than nine hours in custody, looking stone-faced as he refused to comment to a waiting pack of reporters. despite crushing pressure on him to resign.

"It's Kafkaesque," said veteran Montreal city Councillor Marvin Rotrand, who said he was in shock at the arrest. "People are really wondering what is going on at Montreal City Hall. This fosters cynicism even more."

The list of big-city mayors under suspicion continues. Laval's Gilles Vaillancourt, long-time mayor of Quebec's third-largest city, was arrested last month and charged with fraud and gangsterism. And the mayor of Toronto is under a cloud in connection with an alleged video that appears to show him smoking crack cocaine.

"What the Heck Is the Matter with the Mayors of Canada?" asked The Atlantic magazine, one of dozens of media outlets around the world to report Mr. Applebaum's arrest. "What, exactly, is going on with our unassuming northern neighbors? There's something rotten not in Denmark, but in Canadian cities across the country."

The charges against Mr. Applebaum date to when he was mayor of the western Montreal borough of Côte-des-Neiges–Notre-Dame-de-Grâce. The province's anti-corruption police unit, known as UPAC, says the charges relate to two real-estate projects in the borough between 2006 and 2011, and involved bribes worth tens of thousands of dollars.

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"No one is above the law and you can't hide from the law," Robert Lafrenière, head of UPAC, told a morning news conference.

Two other figures were also charged and arrested Monday. One is Saulie Zajdel, a former city councillor who ran for the federal Conservatives in 2011 and worked in a ministerial office for the Tories. The other is Jean-Yves Bisson, former borough manager.

Mr. Applebaum's arrest placed him under intense pressure to step down and leave stewardship of city hall to its ruling coalition until Montrealers head to the polls in November. In the wake of his arrest, Mr. Applebaum lost political support even from former allies.

"Under the circumstances, it would be preferable that he withdraw from the function he now occupies," Quebec Premier Pauline Marois said, adding her voice to a unanimous chorus that included opposition leaders at city hall.

The Premier ruled out trusteeship for the province's biggest city, however, because members of the coalition are not touched by the allegations. "There is no reason that justified that we put Montreal under trusteeship at the moment," she said. Neighbouring Laval was placed under trusteeship this month.

Others saw cause for further erosion in public trust in its institutions, at a time when the Charbonneau Commission continues to feed the public a daily diet of backroom deals and corrupt practices in the awarding of public works contracts.

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Ironically, Monday's arrest arrived at a time when Montrealers appeared satisfied with Mr. Applebaum and his coalition at city hall. The mayor had made corruption a central concern in his administration, and a recent poll showed two-thirds of Montrealers were satisfied as a result.

Mr. Rotrand, who introduced Mr. Applebaum to municipal politics and has known him for 20 years, said he had a hard time believing the charges. "This is not the Michael Applebaum I have known, who is an honest politician who doesn't cut corners and works for citizens."

Despite Mr. Applebaum's cleanup efforts, he was dogged by questions about his tenure in his former borough. Police raided the borough offices as well as Montreal City Hall this year; in March, a senior borough manager, Robert Rousseau, died by suicide a day after being questioned by UPAC investigators.

The turmoil has focused attention on the November vote, which is attracting a fresh field of candidates. In addition to two opposition parties at city hall, new entrants include former Liberal MP Denis Coderre; Montreal lawyer Mélanie Joly announced her candidacy Monday and high-profile Montreal economist Marcel Côté is said to be ready to jump into the race this week.

Candidates began positioning themselves for the city's top job as they responded to Monday's arrest. "This is a sad day for Montreal, and nobody is happy about this," Mr. Coderre said, "but we have an alternative."