Thomas Mulcair won't have the NDP brass or the top-ranking members of Canada's union movement at his side when he jumps into the NDP leadership race.

Instead, the deputy leader will present himself on Thursday as a candidate who would seek to expand the reach of the NDP across Canada, in much of the same way the party broke through in Quebec in the last election.

Mr. Mulcair acknowledged in an interview that he faces an uphill battle to catch up to Brian Topp, the long-time party strategist who has won the support of former NDP leader Ed Broadbent and the official endorsement of the United Steelworkers, among others.

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Still, Mr. Mulcair said he will use the leadership race to present a plan for the NDP to come to power in 2015.

"It was quite clear from the early days that a lot of the party brass were going to rally behind a candidate that they wanted to put in place, but the whole purpose of a leadership race is to put everything on the table and say what your vision is, how you think the party can grow, and where," he said in an interview.

Mr. Mulcair said he has proven his ability to beat the odds in the past, winning a by-election in the Liberal stronghold of Outremont in 2007, and then becoming the first NDP candidate to win a Quebec seat in a general election.

"The purpose of this exercise is to find out who can defeat Stephen Harper in the next election and put a government in place that is more in harmony with the views of the over 60 per cent of Canadians who did not vote for the Conservatives in the last election," he said.

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Mr. Mulcair said he is well aware of the importance of the labour movement in the NDP, but he also made clear that his bid will rely on support from other groups.

"We have to recognize the importance of the work .... and the heavy lifting done by the union movement to help the NDP, but I also know that we have to connect with Canadians as widely as possible, and that the only interest we should be serving is the public interest," he said.

In particular, Mr. Mulcair said he wants to lead a fiscally prudent government.

"We have to convince people that the NDP is capable of providing top-quality administration of their money, in the public interest," he said.

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