As the eldest son of former prime minister Pierre Elliott Trudeau, Justin Trudeau followed the family name into politics. And the Trudeau family name will be prominent in the campaign to secure his father's old job as Liberal leader.

On Oct. 2 in his Montreal riding of Papineau, Mr. Trudeau will announce his candidacy for the party leadership, several sources say. And for the family, the date is significant.

It's the birthday of Mr. Trudeau's youngest brother, Michel, who died in an avalanche at the age of 23 while skiing in B.C.'s Kokanee Glacier Park 14 years ago.

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Mr. Trudeau's other brother, Alexandre (Sacha) Trudeau, a journalist and filmmaker who has kept a low profile in recent years, will leap into politics as a senior member of the campaign advisory team.

Mr. Trudeau married television host Sophie Grégoire in 2005 and has often described her as a key source of political advice. The couple have two children, Xavier and Ella-Grace, born in 2007 and 2009, respectively. It is not yet known what role Mr. Trudeau's mother, Margaret, will play.

Beyond the family connections, Mr. Trudeau has lined up an inner circle of advisers with connections to the Ontario Liberal Party and senior aides to recent federal Liberal leaders Paul Martin, Stéphane Dion and Michael Ignatieff.

Mr. Trudeau's summer tour across Canada showed he has no trouble attracting a crowd. The background of his advisers – as well as the topics of his speeches – suggest campaign themes focused on middle-class economics, the environment and training young people for future jobs.

While Mr. Trudeau's family is central to his campaign, opponents are raising the unpopular aspects of his father's record during his time as prime minister – from 1968 to 1979 and then from 1980 to 1984.

The Liberal Party – which lost most of its rural seats in recent years and has not fully adapted to fundraising without corporate donations – faces major logistical hurdles to overtake the NDP and challenge the Conservatives for power. So far, only a handful of little-known candidates have entered the leadership race. The question is whether Mr. Trudeau's candidacy will deter bigger names – including MPs Marc Garneau, Dominic LeBlanc and Denis Coderre.

PEI Liberal MP Sean Casey says the party needs a contest. "I don't think a coronation is good for the party," he said. "I think it's clear that Justin has widespread appeal, but I expect and I hope that there will be others."

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Mr. Trudeau's campaign is expected to be managed by Katie Telford, a deputy chief of staff to Mr. Dion when he was Liberal leader who has also worked for the Ontario Liberal government. Mr. Trudeau will also rely heavily on Gerald Butts, the chief executive officer of World Wildlife Fund Canada and a former principal secretary to Mr. McGuinty. Mr. Trudeau's relationship with Mr. Butts dates back to their years at McGill University, and they have been discussing Mr. Trudeau's political career for more than a decade, a source said.

Mr. Butts is currently travelling through B.C.'s Great Bear Rainforest, which would be affected by the proposed Northern Gateway pipeline from Alberta's oilsands to the Pacific Coast. WWF is a fierce opponent of the project, and Mr. Butts' involvement in the leadership campaign signals that Mr. Trudeau will dedicate a portion of his platform to environmental issues. University of Ottawa professor Robert Asselin, who was a speechwriter for Mr. Martin and Mr. Ignatieff, is also among the campaign advisers, as is Vancouver-based lobbyist Bruce Young, who was Mr. Martin's senior adviser for B.C.

With the team in place, it's clear Mr. Trudeau has made up his mind. When and why the decision was made isn't clear. Mr. Trudeau had said he wanted to spend the summer discussing the idea with his family.

Mr. Trudeau travelled extensively this summer in a campaign-style tour. One Liberal said Mr. Trudeau heard from many Liberals urging him to run, and many who said they would work to support him.

"He's still is the only Liberal who can go into rural Alberta or British Columbia or Saskatchewan – or anywhere else in this country, péquiste corners of Quebec – and turn out 200 people to hear about the Liberal Party. There's no one else who can do that and it's remarkable to watch when you see it firsthand," one Trudeau supporter said.

In many ways, Canadians have known Tuesday's announcement was coming since October, 2000.

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"There's been tremendous pressure on Justin to run since the eulogy," Liberal MP Rodger Cuzner said, in reference to the speech Mr. Trudeau gave at his father's funeral.

The speech – which attracted both praise and criticism – began with a quote from Shakespeare's Julius Caesar, "Friends, Romans, countrymen" – and inspired a stream of speculative news features over the years about Mr. Trudeau's seemingly inevitable campaign for the Liberal leadership. In a 2002 interview with Maclean's, Mr. Trudeau spoke of this in terms of "when," not if.

The Trudeau name is a double-edge sword, as other political parties are already using the legacy of Mr. Trudeau's father as part of their efforts to undermine the Liberal brand.

Maxime Bernier, the junior minister of tourism and small business in the Harper government, said Mr. Trudeau will not be able to escape the low points of the Liberal government in the late 1970s and early 1980s, which fuelled Western alienation and piled on debt.

"It risks reminding Canadians about his father's record," Mr. Bernier said of a Trudeau candidacy. "The National Energy Policy was a disaster in Canada, and there are other policies, so we'll see what happens."

The family name could also hurt Mr. Trudeau in Quebec, where sovereigntists have spent decades attacking the unilateral repatriation of the Constitution by his father's government as a betrayal of the province.

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However, Mr. Trudeau has quieted many doubters about his ability to win in Quebec by launching his political career in the multi-ethnic riding of Papineau in the centre of Montreal instead of a safer anglophone enclave in the western part of the city.

Mr. Trudeau won a contested Liberal nomination for the riding, took the seat away from the Bloc Québécois in 2008 and held on to it last year, showcasing his ability to win hard-fought races.

Editor's note: An earlier version of this article incorrectly spelled Alexandre (Sacha) Trudeau's name. This online version has been corrected.