"This race is like no other," the Ontario provincial politician and former Winnipeg mayor said during a news conference at the famed Maple Leaf Gardens where he announced his candidacy.
"The winner of this race will be the premier of a minority government with an opposition set to force an election. This race is about picking someone who has a clear agenda and a premier who is ready if forced to take the Liberals into election and win another mandate."
Murray, 55, broke the news a day after stepping down as Ontario minister of training, colleges and universities — fulfilling a prerequisite set out by McGuinty who wanted any minister interested entering the race to first quit cabinet.
McGuinty announced on Oct. 15 that he was leaving public office after nine years as premier and 16 years as party leader.
Surrounded by family and friends, Murray said his experience as a big-city mayor and at the Ontario legislature gives him the confidence to take the reins of the party, which has struggled since forming a minority government in the last provincial election.
Murray said he is proud to be a Liberal but agreed that it was time to "reset" and renew the party.
"We are a great party of ideas, of action and certainly of achievement," he told a cheering crowd.
"I have new ideas to renew our vision."
"If chosen to lead the party, Murray promised a five-point platform centred on tax cuts for small businesses, up to $500 in tax rebates for middle-income families and a "no-money-down" tuition-fee program for college and post-secondary education.
Under his guidance, he said, students would not have to put down a deposit of thousands of dollars before starting their studies.
Murray maintained that these lofty promises could be accomplished through turning current tax deductions into grants, and promoting more productivity in government.
When pressed about specifics, he maintained that it could be done despite the province's inflated $14.4 billion deficit.
"I will reconcile all of these numbers," he said. "You will have more spreadsheets. As you know, I am not a person who is accused of being short on words or details. I will try to be a little more concise."
Murray, the first openly-gay mayor of a major Canadian city when he was in charge of Winnipeg from 1998 to 2004, is considered a trailblazer not only in politics but in social activism.
He has long played a role in the lesbian, gay, bisexual, and transgender community (LGBT) and is credited with being one of the founding members of the Canadian AIDS Society.
Murray also worked as the chair of the National Round Table on the Environment and Economy and as President and CEO of the not-for-profit organization, the Canadian Urban Institute.
He won a seat in the Ontario legislature in a 2010 byelection in Toronto.
"I've been a big-city mayor, I have successfully led a large government through similar challenges to the ones we face now," he said, adding he did so by working with people "of all political stripes."
He said he didn't want to brand himself as a Toronto-centric candidate, and pointed to family roots in Sudbury and Alexandria, Ont.
Murray told reporters he has support from his cabinet colleagues even though none of them were present at his Sunday launch.
Those in the room to support him included his mother, partner of 17 years Rick Neves, former Research in Motion co-CEO Jim Balsillie and Toronto mayoral candidate and former provincial Liberal cabinet minister George Smitherman.
Both the Progressive Conservatives and the NDP bemoaned Murray's bid for leadership, citing that it will lead to much of the same policies the province has seen under McGuinty in the past years.
"Glen Murray can hit the 'reset button' until his finger hurts, but people won't forget he's part of the McGuinty Liberal status quo," said Gilles Bisson, a New Democrat member of the legislature.
Progressive Conservative Rob Leone said Ontario needs a leader who can rein in public spending.
Murray dismissed suggestions that he was trying to steal thunder from his colleague, former Municipal Affairs Minister Kathleen Wynne, who was set to launch her campaign Monday.
Wynne, who is also an openly gay politician, resigned from cabinet last week.
"We were on track. This was our plan," he said. "It wasn't about being first. It was about being ready."
The Ontario Liberal Party will elect their new leader at a convention at Maple Leaf Gardens on Jan. 25.
Other potential candidates said to be considering a bid include former cabinet ministers Sandra Pupatello and Gerard Kennedy, who lost to McGuinty by just 140 votes in 1996.
Some high-profile members in McGuinty's caucus have already rejected the idea of replacing him.
Finance Minister Dwight Duncan, Energy Minister Chris Bentley, Education Minister Laurel Broten and Economic Development Minister Brad Duguid have all decided to stay out of the race.