TORONTO - Former Ontario Progressive Conservative leader John Tory, a wealthy former executive and adviser to ex-prime ministers Brian Mulroney and Kim Campbell, won't be taking another shot at leading Canada's most populous city.

Tory, who became a talk-radio host after quitting provincial politics last spring, announced Thursday that he won't run for Toronto mayor in the Oct. 25 municipal elections.

Brushing off suggestions that he may be in line for a Senate seat instead, Tory said he has no plans to seek elected office in the future.

But that doesn't mean he's done with politics for good, he said.

"I have been around politics for 40 years, 35 of them as a volunteer," Tory said.

"And one lesson I've learned -- some I probably didn't -- but I learned the lesson that you never say never. You never say it's absolutely, positively over."

Yet some believe it's unlikely that Tory, who had a rocky run leading the Ontario Conservatives, will ever return to politics.

"I think he's done," said one supporter, who spoke on condition of anonymity.

"I think he views this as, 'Thank you, all right, I've had enough drama with the public for awhile. They'll be tired of me."'

Tory, who quit as party leader after a humiliating byelection defeat last spring, had been mulling another shot at Toronto's top job for months, despite losing in 2003 to current mayor David Miller.

Going head-to-head against ex-deputy premier George Smitherman, who hasn't yet formally entered the race, wasn't a factor in Tory's decision to remain on the sidelines, the source said.

Polling showed that Tory had a significant lead over Smitherman, the source said. He also had the support of between 15 to 20 of the city's 44 councillors while Smitherman had only one on his side.

But experts predicted Tory would have to overcome being branded an electoral loser after a disastrous 2007 provincial campaign, a defeat that was largely blamed on his controversial proposal to extend public funding to religious schools.

He also failed to win a seat in the legislature, which fuelled an internal party revolt and grumblings that he was too indecisive and unwilling to listen to advice.

After more than a year of wandering in the political wilderness, Tory was finally given a shot to run in a rural central Ontario riding last March. He lost to Liberal rookie Rick Johnson and relinquished the Conservative crown soon after.

The possibility of losing another election after his troubled stint as party leader didn't influence his decision to stay out of the mayor's race, Tory said.

"If I could end my own life and have my children know that I was an honest person of integrity who was competent and made a contribution to his community, I'd be very happy with that, and I won't be sitting around on those last days wondering about what if I'd done such-and-such in the 2007 election," he said.

"This stuff is important. I let some people down a bit, but it's pretty small potatoes in the context of your overall life."

He plans to continue his radio show and take the helm at the Toronto City Summit Alliance, a job previously held by David Pecaut, who co-founded Luminato, a successful arts festival in the city.

He will also continue with his "increased responsibilities" at the Rogers business empire since the death of his friend and mentor Ted Rogers, as well as his work on other corporate boards and charities, he said.

The race for mayor, which officially began Monday, has attracted other high-profile candidates including Rocco Rossi, the former national director of the federal Liberals.

Rossi, who ran Tory's 2003 mayoral campaign, said the city has lost a good candidate.

"I know he's going to continue to make a huge contribution in the life of the city because that's just the kind of guy he is," he told CFRB, the Toronto station that broadcasts Tory's show.

Smitherman called Tory a "great Torontonian."

"I respect John a great deal, especially for the contributions he's made to the city I hope to lead," he said in a statement.

"I can think of no better person to work to bring Toronto's businesses, not-for-profit organizations and governments together."

Smitherman is expected to register for the mayor's race soon, after giving up his provincial seat Sunday.

Eleven people have signed up for the race, including Coun. Giorgio Mammoliti, who served in the Ontario NDP government of Bob Rae. Two other city councillors -- Adam Giambrone and Rob Ford -- are also mulling a possible bid.

Now that Tory has pulled out, more right-leaning candidates are expected to come out of the woodwork.

Candidates have until Sept. 10 to file the necessary paperwork for the election.