Trudeau is considered the frontrunner in the race to take over the federal Liberals.
While he's often criticized for not having much experience or solid policy knowledge, the son of former prime minister Pierre Trudeau has proven popular with voters, drawing crowds across the country.
Recent polls suggest the Liberals have surged ahead of the NDP and even the governing Conservatives.
But New Democrat MPs downplayed the threat Trudeau could pose.
The next federal election is still two and a half years away. And the Liberals also surged in popularity after selecting Stéphane Dion and Michael Ignatieff as leaders. The party lost seats in subsequent elections under both leaders.
"That he has some type of a little star system, I'll grant that to Justin Trudeau," said Françoise Boivin, a New Democrat MP from Gatineau, Que., across the river from Ottawa.
Boivin likens the Liberals to "an empty book" putting on a different cover.
"It's still a boring book. If you keep changing your trailer about a bad movie, it's still a bad movie... This [the NDP] is organization on the ground. This is different than Facebook friends."
Young MPs could be key
The NDP's "orange crush" that made them the Official Opposition and now gives them 100 MPs in the House of Commons also brought in a substantial contingent of young MPs — not just under 40 years old, but under age 30. Many of them campaigned for party leader Tom Mulcair before he was elected to the House in a 2007 byelection.
Those MPs could be key in keeping the NDP looking dynamic under a leader who can seem gruff and serious. Many of them have critic and committee positions that regularly put them in front of cameras, like Charmaine Borg, 23, the critic for digital issues, or Pierre-Luc Dusseault, 21, who chairs the House ethics committee. And of course there's the over-30 crowd, including deputy leader Megan Leslie, deputy ethics critic Alexandre Boulerice and House leader Nathan Cullen, who all get regular speaking time in question period and on panels on the politics shows.
"I think at the end of the day it's about a team, right? You get Mr. Mulcair, that has a specific style. It's a leadership style, it can be a serious style, but I think that's a positive thing," said Matthew Dubé, the 24-year-old MP for the Montreal-area Chambly-Borduas riding and the party's critic for amateur sport.
"I think we all have our roles to play — to have all these young MPs that can go all over the country and interact with young people and get them involved in the debate. It's not just talking to them, it's talking with them."
"[Mulcair] hasn't been afraid of giving us young MPs those responsibilities to do that outreach and to do that work... it's one thing to be a younger leader, but also the respect that Mr. Mulcair has for young people and what they bring to the debate in Canadian politics means a lot to those people and that's what we believe is important going forward."
Comparisons between Mulcair and former party leader Jack Layton, who died in 2011 after leading the party to its best-ever election result, are rarely made, a year after his leadership win. But "Jack," who was popular with voters, inevitably comes up during the convention.
"People say Jack was inspiring and that changed the game. But Jack was coming to people and giving them concrete solutions. In Quebec, we've spent decades building our positions on Quebec," said Mylène Freeman, who is 24 and the MP for Argenteuil-Papineau-Mirabel, Que.
"And that's what made the breakthrough in 2011. Jack was able to bring that message through having such great, outstanding charisma. But it wasn't just that. You need to have something that Canadians can believe in."
'A party that's in conflict'
Concrete solutions are something the NDP obviously believe the Liberals don't have.
But Liberal MP Marc Garneau, who was an observer at the NDP convention in Montreal this weekend, says the New Democrats have their own challenges.
Garneau ran against Trudeau for the Liberal leadership before dropping out of the race to support him, but repeatedly criticized Trudeau for being light on policy.
The NDP, Garneau says, has grassroots members who aren't comfortable with free trade and don't want to develop the oilsands.
"It's a party that's in conflict over many particularly important files, so it's a real challenge for that party to present a unified image and I think that will harm them over the next two years because they won't be able to convince Canadians they're really capable of responsibly managing the fiscal side, the economy of our country," Garneau told reporters at the convention.
Boulerice says Garneau was right the first time around — when he criticized Trudeau for his lack of policy.
"I think that Mr. Trudeau will see that it's not that easy to be a leader. But, on the other hand, I have to say that it's always a mistake to underestimate your opponent," he said.
Boulerice says it's up to the NDP to show voters they can lead the country.
"It's our job to present Mr. Mulcair as he is, the next prime minister and the best option to run the country," he said.
'Bring it on'
Part of the NDP policy convention has been spent in an attempt to showcase a side of Mulcair that Canadians don't see in question period. A townhall where he took questions from delegates, his keynote speech and several videos were meant to let people get to know him better as a family man and activist in Quebec. But pre-selected questions for the townhall and a speech that focused on policy didn't shed much new light on the party's leader.
In his closing scrum with reporters, Mulcair suggested part of that is due to having spent much of his life in public, through 30 years in a variety of political roles in Quebec.
"Sometimes I take for granted that because I'm a well-known quantity here in Quebec, the same thing applies to the rest of Canada. And the people who work with me say, look, it's worthwhile for you to talk a little bit outside of that," he said as the convention winded down.
"Catherine [Mulcair's wife] and I have always been very careful in our personal lives to maintain some part fo that. Precisely because our kids were young ... Catherine has her own busy career."
Mulcair says they're proud of their kids and understand that part of modern politics involves letting people see a more private side of them.
"We do make sure to do part of that too. But also, at the same time, we think that that's essential to be able to stay in public life that you keep some part of the family life to yourself. So we're trying to get the right mix of both of those."
Boivin says the party has time to let Canadians get to know "Tom the person."
"Leaders are one aspect of it, but our work on the ground, the fact that we're very involved in our communities... bring it on."Suggest a correction