Speaking to a packed church hall, the former city councillor and federal MP — already considered a front-runner — criticized Rob Ford for his "disappointing" leadership.
"He is no role model for my granddaughters," Chow said. "We deserve better."
Chow made no mention of Ford's numerous, highly publicized scandals: crack-smoking, alcoholic binges, profane rants, ties to suspected drug traffickers, and an ongoing police investigation into his activities.
Asked about the potential impact on the mayoralty race of Ford's conduct — the fodder of headlines and TV comedy across Canada and internationally — Chow dodged.
"It's not just a scandal, it's really his failed policies," she said.
Ford, who was stripped of most of his mayoral powers by council, has said he's not concerned at facing off against Chow, bragging instead about his solid fiscal management and dedicated service to his constituents.
"This city's booming, this city's on fire, I've got a proven track record," Ford said Thursday at city hall.
"All she (Chow) is is a tax-and-spend socialist. Everyone knows it. Call it for what it is."
Given his notoriety, what would normally be a local political tussle focused on gridlock, public transit or social housing now seems destined to play out before a much broader audience.
"The world will be watching," said Myer Siemiatycki, a political science professor at Ryerson University.
"The world knows about Mayor Ford and some across the world might wonder, 'Can someone with this kind of record actually get themselves re-elected?'"
Ford's re-election will depend on whether he hangs on to his die-hard supporters, colloquially known as the "Ford Nation," and can pick up votes from those who believe in his self-professed tax-busting record, observers said.
Ford himself was unfazed, saying earlier this week: "My 'Ford Nation' people aren't budging and we're doing great."
Rob Drummond, political science professor emeritus at York University, pegged Ford's bedrock support at somewhere between 20 and 30 per cent.
"I'm astounded at how long he's been able to sustain the support that he has," Drummond said.
To win, Chow will have to hope the conservative vote splits among Ford and his rival right-wing candidates.
Chow, the widow of the late New Democrat icon Jack Layton, is the first heavyweight contender on the left to challenge for the Oct. 27 vote.
What's clear, political observers said, is that she has the pedigree and street cred to be a formidable opponent.
"She brings a very distinctive record, persona, positioning," Siemiatycki said.
Chow's main challenges over the next seven months will be to strip away suburban votes from Ford, and counter perceptions of New Democrats as incorrigibly tax and spend.
In her campaign speech that came a day after she resigned as an MP, Chow shook off any suggestion she's a downtown elite — a phrase Ford often throws at opponents.
She played up her roots as a hardworking immigrant to Canada, noting her speech was given in the same inner city neighbourhood of St. James Town in which she grew up.
"I learned to work hard and make every penny count, to save for rainy days and to invest wisely," she said, adding she helped balance budgets as a councillor.
Nelson Wiseman, a professor of political science at the University of Toronto, said one of Ford's main challenges will be to ensure voters buy into his "ordinary guy" persona.
"Ford isn't the anti-establishment candidate, though he wants to present himself that way. He's actually the mayor," Wiseman said.
"All he can say is that these are downtown elites (but) he drives an SUV Cadillac."
Wiseman also said it's highly likely Ford's recent past will drag him down and out of the race — before voting day.
In addition, Ford might opt to withdraw and run for council if he decides he can't win re-election because a mayoral loss would put him out of politics altogether.
Among other right-wing contenders in the race are one-time Ontario Progressive Conservative leader John Tory, who slagged Chow as someone who "never met a public dollar she couldn't spend," and city councillor Karen Stintz, who called Chow a "double-dipper."
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