After a long eight-month leadership campaign, Liberals are preparing to vote for one of the six candidates they think can best lead the party into the next general election in 2015 following a "national showcase" in Toronto Saturday.

Montreal Liberal MP Justin Trudeau backed-up his perceived frontrunner status with a passionate plea for the party's top job.

Trudeau said he would put forward an "irresistible alternative" to the Conservatives in time for the next general election in 2015, an alternative he described as "100 per cent undeniably Canadian."

He reiterated his promise that every Liberal, incumbent or not, would have to earn his or her own nomination. Trudeau extolled his concern for the middle class, his vision for diversity and federalism.

But his shots at Stephen Harper's Conservatives were sharp-edged and relentless, calling the Tories not so much "mean-spirited" but "unambitious."

For those who have made fun of Trudeau because his job before politics was as a high-school teacher, he said, "let me tell you, this teacher is going to fight back."

He attempted to lay to rest the ghost of his father by bringing up the fact that some have said his campaign is "all about nostalgia."

"They say it's about my father. To them, I say this: It is… It's about all our parents and the legacy they left us, the country they built for us."

Political co-operation

Vancouver MP Joyce Murray and former Toronto-area MP Martha Hall Findlay were seen as vying for second place going into the home stretch of the race, but Hall Findlay conceded she was the "underdog" on Saturday.

And while Murray's plan for a one-time political cooperation with the NDP and Greens was the focus of every debate leading up to Saturday's showcase, it appeared to have little resonance with most Liberals gathered in the room.

Nevertheless, Murray stood firm saying her plan would protect Liberal values and lead to an elected Liberal government.

Hall Findlay suggested she had "the stuff of a prime minister" with the experience and smarts to lead the Liberals in the next general election campaign.

But she also seemed to take a shot at some voters, saying "How many of you noticed, as I did, that the really grumpy people are always Conservative."

Cauchon, Coyne and McCrimmon

Former Chrétien-era cabinet minister Martin Cauchon, touted his years of experience during a time he said the Liberals were the most successful political party in the democratic world.

The candidate from Quebec took a veiled shot at frontrunner Trudeau, saying, "some will convince you that now is not the time to discuss policy."

Toronto lawyer Deborah Coyne spoke of the need for "bold national leadership" in the face of what she called Stephen Harper's "diminished, insignificant Canada."

She said support for the Liberals didn't decline over successive elections because the progressive vote was divided, but because Canadians didn't know what Liberals stood for any more.

Retired military officer Karen McCrimmon said the party would do well to fight back against possible Conservative attack ads, as she pledged to do. "I will be their worst nightmare," she said, daring the Tories to attack "a woman veteran."

Speaking off the cuff, McCrimmon warned the crowd that the Liberal legacy must not be to "bankrupt our children." It was because she saw the country going in the wrong direction that she entered the leadership race, she said.

Tribute to Bob Rae

Liberals began with a tribute to interim leader Bob Rae who led the party through a difficult period after the 2011 election saw it reduced to third-party status in the Commons.

Liberal Party President Mike Crawley praised Rae for holding up the party at what he called "our most perilous hour." Crawley said that even though Rae never became permanent leader, he "will be regarded as one of the great leaders of the Liberal Party of Canada."

Former prime minister Paul Martin, in his tribute to Rae, said the interim leader has "never failed to rise to the occasion," applauding Rae for recently agreeing to work with the Matawa First Nations as a negotiator or mediator on resource development.

There was no mention of Rae's time in the New Democratic Party, and despite the parade of former leaders, no quotes from Stéphane Dion or Michael Ignatieff.

The crowd-pleaser, by far, was a segment from Rae's skinny-dipping skit with CBC's Rick Mercer, showing aspects of the interim leader never displayed by any party chief before or since, as the pixellated part of the video dissolved into a clear shot of the naked Rae and Mercer jumping into a lake.

Rae said his famous skinny-dipping scene with Mercer happened because his staff wasn't with him that day, and he was glad his mother thought it was funny.

He has said he will stay on as an MP but has yet to decide whether he will run again in 2015.

New leader on April 14

While the Liberal Party said 1,500 supporters were expected at Saturday's event, party officials told CBC News 1,000 tickets had been sold prior to the start of the event.

Some 127,000 Liberal party members and supporters are eligible to vote.

Registered voters attending the showcase were able to vote after the speeches wrapped up. Others will be allowed to vote starting Sunday, online or by phone.

A new leader will be announced on April 14 in Ottawa.

With files from CBC's Leslie MacKinnon and Susana Mas