The Montreal MP said he expects a difficult contest and intends to travel the country over the next few months to build up support.
"People are not just going to vote for flash, they are going to vote for substance," Trudeau told reporters Saturday at a Liberal meeting in Sorel, Que., the first since the race officially began on Wednesday.
"Over the coming months, there are going to be a lot of people challenging each other, challenging each of us as candidates to demonstrate that we have the strength and the conviction to be able to earn the trust of Canadians."
While the contest has only just started, Trudeau has a distinct advantage, having announced his candidacy to much fanfare at the beginning of October. Opinion polls suggest his leadership would give the Liberals a considerable boost.
As of Saturday, he was the only person listed as a candidate on the party’s website.
Three other lesser-known Liberals planning a run also gave their pitch on Saturday: Rene Roy, a farmer from Quebec's Beauce region; George Takach, a Toronto lawyer; and retired Canadian Forces Lt.-Col. Karen McCrimmon.
Some of those candidates may not make it far past the starting gate.
The party has imposed a $75,000 fee for entering the contest. It's to be paid in three instalments, the first due upon registration as a candidate, the last due by mid-January.
McCrimmon, who ran unsuccessfully for the Liberals in Ontario in the last federal election, said she had already raised enough for the first payment and planned to travel the country to generate more interest.
On Saturday she was collecting some of the final signatures to officially submit her candidacy.
"I'm doing this because I hope it will be better for all Canadians to be able to see all the different facets of the Liberal party," she said in an interview.
"If all of us are up there on that stage saying 'look at the talent you have to choose from'... we will gain back the confidence of Canadians."
Others have already declared their leadership ambitions.
They include Toronto lawyer and public policy consultant Deborah Coyne, mother of Trudeau's half sister, Vancouver Crown prosecutor Alex Burton, Ottawa lawyer David Bertschi, Ontario government economist Jonathan Mousley and David Merner, former president of the party's British Columbia wing.
Denis Coderre, a prominent Montreal MP, said the list may get a little shorter in the coming weeks.
"It's clear that Justin is official and there are maybe four or five others who are serious candidates," he said.
"It's not just about getting up to a microphone and declaring yourself a candidate... but I think it's clear that there won't be a coronation (for Trudeau), and that's good."
Two potential challengers for the top job, Montreal MP Marc Garneau, who is widely expected to join the race shortly, and former MP Martha Hall Findlay, who announced her candidacy this week, weren't at the Quebec meeting.
In his speech, Trudeau said Liberals have a lot of work to do to regain the trust of Quebecers — and all Canadians.
Trudeau said he wants to offer a vision for Quebec that's distinct from that of the NDP, which nearly swept the province in the past election.
Quebecers want policies that go "beyond the petty rivalries that have taken up so much of our time in the past," he said.
"They want people to be beyond that and that's very much what I'm excited about delivering."
The leadership vote will be held next April.
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