Voting began shortly after the six leadership contenders made their final sales pitches at a "national showcase" on Saturday.
It offered Liberals the only glimpse they're going to get of the excitement and suspense of a traditional leadership convention.
For the coming week, the leadership contest will effectively go underground, as Liberals cast preferential ballots — online or by phone — from the privacy of their homes.
Some 127,000 Liberal party members and supporters are eligible to vote. The results will be announced next Sunday in Ottawa.
The outcome has been widely seen as a foregone conclusion since Justin Trudeau launched his campaign last October, and Saturday's showcase only served to cement his status as the prohibitive favourite.
Trudeau's grand entrance, accompanied by throbbing music and throngs of chanting, placard-waving supporters, was in stark contrast to the subdued demonstrations staged by the other five dark horse contenders.
The front-runner used his final pitch of the leadership race Saturday to launch a pre-emptive strike against the Conservative attacks that are inevitably coming should he win, as expected.
He tackled head-on those who sneer that he's inexperienced, that his resume is light and that his popularity is fleeting, based on nostalgia for his late father, former prime minister Pierre Trudeau.
"There are those who ask me: 'What makes you think you can take this on?'" Trudeau told the assembled Liberals.
"To them, I say this. I have lived and breathed every square kilometre of this country from the day I was born ... I have been open to Canadians my entire life and, because of that, I have a strong sense of this country — where it has been, where it is and where Canadians want it to go."
The 41-year-old Montreal MP noted that Saturday marked the 45th anniversary of his father being chosen to lead the Liberal party.
"I know there are those who say this movement we're building is all about nostalgia, that it's not really about me, or you, or Canada. Let's face it, they say that it's about my father," Trudeau acknowledged.
"Well, to them I say this: It is. It is about my dad ... It's about all our parents and the legacy they left us, the country they built for us," Trudeau said.
"It's more about the future than the past, it is always, in every instance, about our children more than our parents' legacy," he added.
Trudeau's critics — including some of his leadership rivals — have suggested his background as a school teacher, snowboard instructor and public speaker before entering politics in 2008 has left him ill-prepared to lead the party, much less govern the country.
But the Montreal MP scoffed at what he termed "Conservative attacks on teachers."
"I am fiercely proud to be one of the hundreds of thousands of Canadians who belong to the teaching profession. And let me tell you this, my friends, this teacher fully intends to fight back."
None of Trudeau's rivals dared make any direct attacks on the front-runner, whose supporters dominated the crowd at Saturday's showcase.
However, former Toronto MP Martha Hall Findlay indirectly alluded to Trudeau's alleged lack of experience and gravitas by asking Liberals to imagine which candidate would be best equipped to sit down with international leaders or square off against Prime Minister Stephen Harper and NDP Leader Tom Mulcair in televised debates during the next election.
"You know that we will need someone on that stage who is experienced, clear, firm, decisive, no-nonsense and tough," Hall Findlay said, casting herself as a "business conscious, market-oriented" Liberal who is "substantive, experienced, bold, tough."
The showcase was replete with chanting supporters, thunder sticks, placards and all the usual paraphernalia of a political convention, although long-shot contenders had a tough time garnering more than a smattering of applause in a cavernous hall at the Metro Toronto Convention Centre.
The hall, which seated 1,500, was not quite filled to capacity.
Organizers with various camps privately conceded after the showcase that the event was unlikely to have changed many voters' minds.
Joyce Murray, who is widely thought to be running second, pitched her plan for one-time electoral co-operation among progressive parties in the 2015 election to ensure defeat of Stephen Harper's Conservatives — a proposal which has drawn the fire of her rivals but helped the Vancouver MP stand out and gain support from grassroots and online advocacy groups.
She likened her idea to hockey players who come together to win gold for Canada during the Olympics but then return to their various teams and resume being fierce competitors.
"This is not a merger, this is not a coalition, not a joint party candidacy," she told the crowd, trying to dispel doubts. "Our party's distinct Liberal values and Liberal identity will be honoured and protected."
Nor is the motivation to win at all costs, as Trudeau and others have asserted, Murray added.
"I'm talking about winning the next election for a purpose: to reform Canada's ailing electoral system to create a more representative and more collaborative Parliament."
While he largely ignored his leadership rivals, preferring to direct his fire at Harper and Mulcair, Trudeau did use his final speech to reject Murray's co-operation plan in the harshest terms yet.
He said it would create a "Frankenstein's monster" of Liberals, New Democrats and Greens that would be "at war with itself over fundamental issues like the Constitution, natural resources and free trade."
"The truth is," he added, "Canadians want to vote for something, not just against somebody."
Toronto lawyer Deborah Coyne, who has openly conceded she can't win, also dumped on Murray's co-operation idea as an unprincipled bid to regain power without earning it.
"As long as Liberals look for short-cuts, we are doomed to wander in the wilderness," she said.
Coyne, meanwhile, revealed what may have been the real motivation behind her long-shot leadership bid, announcing that she intends to seek a nomination to run in the next election and looks forward to being part of the Liberal team.
"Several new ridings are being created in the Toronto area and I think you will agree with me that we should have strong women candidates contest these ridings," she told the crowd.
Coyne has run unsuccessfully for the Liberals in the past, a sacrificial lamb who went up against late NDP leader Jack Layton.
Retired military officer Karen McCrimmon, another failed election candidate who may be hoping to raise her profile before trying again to win a seat in the House of Commons, was escorted to the stage by a lone bagpiper.
Much like a motivational speaker, she strode back and forth across the stage in a white pant suit and spoke without notes. McCrimmon acknowledged she often wondered if she was "crazy" to have launched her leadership bid. But she said she followed her heart and urged Liberals to do the same.
"The Liberal party has to stop listening to the naysayers," she said.
Former cabinet minister Martin Cauchon was the last to speak at the four-hour showcase, which also featured a tribute to interim leader Bob Rae. Rae has held down the fort since the Liberals were reduced to third-party rubble in the May 2011 election.
Although each camp was allotted 100 tickets for the event, Cauchon appeared to have brought only a handful of supporters with him. By the time he took the stage, the crowd had begun to trickle out.
Still, he gamely insisted he's the best choice to stand up to Harper.
"I'm not afraid of the attack ads," Cauchon asserted.
"If I become leader of our party, Stephen Harper, I'm going to take you on and Canadians are going to bring you down. Trust me."
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