Adam Giambrone’s meteoric rise through Toronto politics crashed dramatically after he apologized for a sex scandal and an aide pronounced: “His mayoralty campaign ends today.”

The unbelievable scene in a City Hall committee room was triggered by a sex scandal broken Tuesday morning in the Star, and followed a day of denials and then an admission that he lied to the newspaper over his relationship with a university student and in fact has had multiple affairs.

Looking uncharacteristically haggard, the tall, baby-faced TTC chair stepped to a microphone in front of dozens of journalists and began: “There are weeks that change your life and this one has certainly changed mine.

“This searing experience has taught me, permanently I hope, that a public career of integrity cannot survive deceit in your private life,” he said.

Giambrone then offered an apology to his live-in girlfriend Sarah McQuarrie, his family, friends, supporters, the “women I have treated disrespectfully”, his council colleagues and to the “young people who believed in me.

“It is my sincere hope that they will continue to believe in themselves and their ability to make positive change,” he said.

Hi continued: “Finally, I deeply apologize to my partner Sarah. The pain she has endured for my mistakes was deeply unfair to her. She has shown a lot of strength in all of this.”

He then said, “Thank you,” and, as reporters hurled questions about the fate of his 10-day-old mayoral campaign, turned and walked out the door, into a stairwell and down toward the parking garage with a phalanx of city staffers and security guards around him.

Later, insiders suggested he was mistakenly handed just one page of his two-page speech.

A short while after the one-minute, six-second appearance, his executive assistant, Kevin Beaulieu, returned and told confused reporters: “In the emotion of the moment Adam was unable to finish the statement and I will read it to you on his behalf. ...”

Beaulieu said Giambrone is going to reflect on the advice he is getting.

“He will spend the next few days in private; his mayoralty campaign ends today,” the aide said.

“Beginning next week he will return to his normal duties as city councillor. He will focus with renewed energy on the transformation of the TTC and on building Transit City for the people of Toronto. Adam would like to thank all his friends and his supporters who have helped him through these painful days.”

Last week, after a profile of Giambrone by the Star’s Linda Diebelthat included McQuarrie, Kristen Lucas, 20, contacted the paper to say she had an affair with Giambrone that started in late 2008 when she was 19.

She said it included late-night sex on his City Hall couch, text messages portraying McQuarrie as window-dressing for his political career and Giambrone telling her about a TTC fare hike long before it was made public.

Giambrone initially admitted an “inappropriate relationship” with her but said it was limited to text messages and public outings. On Tuesday night, faced with mounting evidence he had lied, Giambrone admitted to multiple relationships in the past year.

In a statement to the Star he said he had “broken my own moral code and offended the values I was raised with by my parents ... I apologize to those I have hurt by my decisions. In the period ahead I pledge that I will do everything possible to live by the lessons learned in this scarring experience.”

Reaction from Giambrone’s stunned colleagues was a mixture of regret for a young, promising career so publicly damaged, concerns over his continued chairmanship of the already reeling TTC, and speculation over how this affects the mayoral race.

Mayor David Miller, in Ottawa for a municipalities’ meeting, issued a terse news release stating: “Councillor Giambrone’s decision to leave the mayoralty race is regrettable. His voice and the vision he could have brought to this important campaign will be missed but his decision to focus on his private life and his current duties is understandable.”

Deputy Mayor Joe Pantalone, who was Giambrone’s rival mayor candidate from Miller’s left-wing faction of council, said it’s “not a happy moment to for anybody who is young and smart and up and coming and willing to contribute to fall this way.”

But Pantalone said there is no need for Giambrone to step away from the TTC, which is reeling from rider discontent and embarrassing photos and videos of workers.

“We cannot kick somebody who is down – it is not the human thing to do, it is not the Torontonian thing to do. Let him get up and learn from his mistake.

Pantalone added that Giambrone’s departure from the mayoral race “obviously simplifies the choice for Torontonians – but that’s not the way I wanted it to happen.”

Other councillors were privately saying Giambrone’s departure creates a vacuum on the left, and were wondering if Coun. Shelley Carroll – a woman from the suburbs who heads the budget committee – might change her mind and run.

Calls to Carroll after Giambrone’s announcement haven’t been returned.

Coun. Howard Moscoe, a former TTC chair, said Giambrone “probably did the right thing in pulling out of the mayoralty race” but added, “I don’t think this will affect his ability to lead the TTC.”

Moscoe added: “I’m not sure there are many single males in this city who could have their hormones closely examined.”

Kyle Rae, who represents Toronto Centre-Rosedale, said Giambrone’s admission was “shocking to me. I had no idea.” He said Giambrone got too hands-on with the TTC, at the expense of other council duties, but said the decision on whether to remain chair rests with him.

Two members of council’s right-wing faction renewed calls for Giambrone to step down from the TTC, accusing him of mismanagement.

“One has to ask oneself, and it’s a very fair question, does he have the confidence of the public to see us through and bring about change at the TTC,” said Denzil Minnan-Wong (Don Valley East).

Rob Ford, who himself has been embarrassed by public indiscretions, said Giambrone did the right thing by ending his mayoral hopes and “he should have resigned from the TTC months ago.”