TORONTO — A left-leaning politician popular in liberal downtown Toronto kicked off her campaign to replace Rob Ford on Thursday, setting up a showdown with the conservative mayor who vows he will win despite the drug scandal engulfing him.

Olivia Chow, who resigned from her Parliament seat earlier this week ahead of her campaign launch, made no mention during her speech of the incidents of drug use, drunken public appearances and erratic behavior that have given Ford international notoriety. But she said the mayor has disappointed his city.

“The current mayor is failing at his job, and he is no role model for my granddaughters,” Chow said at a packed church hall. “We deserve better. It’s time for a change.”

A Hong Kong native who emigrated to Canada when she was 13, Chow is the widow of Jack Layton, the leader of the leftist New Democrat party who died of cancer in 2011. She is the only prominent left-leaning candidate in a crowded field of right-of center contenders in the Oct. 27 election.

Ford has rebuffed pressure to resign since admitting to smoking crack cocaine last year. The Toronto City Council stripped him of most of his powers in an effort to isolate him but it lacked the authority to force him out.

Ford has said he is not concerned about the challenge from Chow, whose candidacy was widely expected. He insists he remains highly popular in Toronto’s working-class conservative suburbs, which carried him to victory in 2010, galvanized by his promise to shake things up at a City Hall he said was dominated by free-spending liberal elites.

Chow, 56, and her late husband formed a political power couple for decades. The NDP, a union-backed party with socialist roots, took Canadians by surprise in the May 2011 federal election by winning official opposition status for the first time, sidelining the long-dominant Liberal Party. Many credited Layton’s charisma and popularity. He died a few months later.

Chow, a former Toronto city councilor who has spent 26 years in politics, emphasized her immigrant roots during her speech, dismissing attacks from the Ford camp that she will spend recklessly if elected mayor. Promising to keep Toronto’s budget balanced, as required by law, Chow said her humble upbringing taught her about the value of money and working hard.