TORONTO - Ex-Winnipeg mayor Glen Murray has abandoned his bid to become Toronto's top politician Thursday and will instead seek to replace former Ontario cabinet minister George Smitherman in his downtown Toronto riding.

Smitherman is expected to vacate his seat in the new year to pave the way for his 2010 run to become Toronto's next mayor.

Murray confirmed Thursday that he'll seek the Liberal nomination in the provincial riding of Toronto Centre, removing him as a potential rival for Smitherman in the mayoral race.

The 52-year-old said he made the decision to jump into provincial politics after testing the waters by talking to "close to 2,000" people.

"It was really becoming pretty clear that a lot of folks thought working together we could make a pretty big difference if I was to stand as a candidate for the Liberal nomination in Toronto Centre," Murray said in an interview.

Smitherman, who served as health minister and energy and infrastructure minister, is expected to launch his campaign next year. Former Progressive Conservative leader John Tory is also expected to run, but hasn't yet announced his intentions.

Smitherman, one of Ontario's first openly gay politicians, resigned from cabinet last month but has yet to give up his seat, a riding represented federally by Liberal Bob Rae, who once served as Ontario's NDP premier.

"Toronto Centre is one of the most diverse parts of Ontario," Smitherman, who held the riding for a decade, said in a statement.

"I am supporting Glen Murray because his work, whether as a big city mayor or a public policy leader, has always been focused at the local community level."

Murray became the first openly gay mayor in a major Canadian city when he won the Winnipeg race in 1998. He left the post in 2004 and took a run at a Manitoba seat in the 2004 federal election, but lost to Conservative Steven Fletcher.

Murray, whose partner is a nurse in one of the city's big hospitals, has lived in Toronto for about six years and is currently chief executive of the Canadian Urban Institute.

He's served on Premier Dalton McGuinty's advisory panel on climate change for about three years, as well as an advisory group on how to manage growth in a great swath of southern Ontario called the Greater Golden Horseshoe.

The environment, poverty and urban issues are all close to his heart, he said. But it was McGuinty and his support for public transportation projects and green energy that inspired him to return to public life.

"I've always viewed politics not as a job, but as an act of public service," Murray said.

"You make a decision when it's hard on yourself. Your family gives up a lot, you're very rarely home, you're out in the community every night working with volunteers and supporting the people who elected you."

There are a few factors that were likely behind Murray's change of heart, insiders say, including the possible slate of rival mayoral candidates.

"He's only lived in the city for six or seven years, and to run for mayor in a city of 2.5 million, having only lived here for a period of time, is a bit of a stretch," said one Liberal source.

"And running for mayor also requires you to raise probably between $1 million and $1.5 million, and that's a lot of work."

Murray, who's already been tabbed as cabinet material, is better known locally and his experience as a downtown mayor will be a big asset in the upcoming byelection, the source said.

He's worked on AIDS-related issues and helped new immigrants in the city, which will translate well in an urban riding that's home to thriving gay and immigrant communities, the Liberal source said.

"It's probably a much better fit," the source added.

He's also very good at bringing different groups together and building teams, and has great cabinet potential, said another source.

"Right now there's some gaps in the cabinet that could use somebody like Glen," the source said.

"My fingers are crossed. ... I mean, he's got an incredible urban brain."

Murray, who was born in Montreal, has much to offer and doesn't like being pigeonholed as the gay politician, said another source.

"The one thing that Glen is always very clear about is that he doesn't want to be the gay candidate," the source said.

"He is a candidate who just happens to be gay."

Murray was considered to be a possible Liberal candidate in the Toronto riding of St. Paul's when former cabinet minister Michael Bryant resigned from provincial politics. Eric Hoskins, a doctor and former adviser to Lloyd Axworthy, ended up with the nomination and easily won the Sept. 17 byelection.

The Progressive Conservatives and New Democrats have not yet named any potential candidates who may run in the yet-to-be-announced byelection.

Toronto Mayor David Miller, who was elected in 2003, announced in September that he would not seek a third term.