Mississauga Mayor Hazel McCallion has plunged into the heated battle to fill her long-held seat, endorsing Bonnie Crombie for the city's top political job.

Ms. McCallion, who is retiring after serving nearly four decades as mayor, expressed her support for the Mississauga councillor and former Liberal MP at a fundraising event for Ms. Crombie on Friday night. A 52-second portion of her remarks was posted to YouTube on Sunday by Ms. Crombie's campaign.

At The Globe and Mail's request, the campaign e-mailed a longer clip of Ms. McCallion's speech. In the slightly more than four-minute video, the 93-year-old mayor praises Ms. Crombie's work as councillor and suggests she's leaving the city "in good hands."

Story continues below advertisement

The popular mayor's endorsement is significant and could alter a tight race between Ms. Crombie and Steve Mahoney, a former provincial and federal Liberal politician.

"I say to you, look at the programs – you have to – of both candidates, the chief candidates that are running, and I have every confidence that when you review it, that you will vote for Bonnie Crombie," Ms. McCallion told supporters of Ms. Crombie in a videotaped speech at the Emerald Chinese Restaurant. Her comments drew loud cheers and applause.

"I'm saying it because of my experience working with her," Ms. McCallion continued. "I leave it up to you. And I say to the young people: Bonnie is young and she's ambitious. She works hard. She's got some new ideas and I hope those new ideas will come forward."

Ms. McCallion could not be reached Sunday for comment about her decision to support Ms. Crombie. Mr. Mahoney's camp said the mayor was on a flight to China.

Story continues below advertisement

In a statement, Mr. Mahoney said he respects the mayor's decision, but noted the election will be decided by voters. "This campaign is not about the status quo. It is about the need for our next mayor to be an experienced leader with a plan to build an even stronger Mississauga, starting the day after election," he said. (Mr. Mahoney wasn't available for an interview because he was with his ailing mother, said his campaign chairman, Quito Maggi.)

Ms. Crombie said she's delighted by the mayor's backing of her candidacy and platform. She had not expected Ms. McCallion to attend the fundraiser, she said, nor to publicly state her support.

She believes it could help persuade undecided voters to cast a ballot for her on Oct. 27.

"I think that it shows that she has the confidence in the platform that I have presented and in my skills as the potential next mayor of Mississauga," Ms. Crombie said, noting she considers Ms. McCallion a role model.