But how the party goes about recapturing its old stomping grounds from the Conservative clutches was a matter of debate in Winnipeg as the leadership candidates squared off against each other on Sunday.
Although the party was essentially born on the Prairies, the NDP only hold three seats in the provinces between Ontario and British Columbia.
"Here on the Prairies, we have our deepest roots but very few trees," candidate Thomas Mulcair said. "In Saskatchewan, our birthplace, we have our deepest roots and no more trees."
In Quebec, Mulcair said it's the opposite, where the party has many trees with weak roots that could be knocked over with a strong wind. The only way the party can build on its success in the last election, he said, is to hold on to those seats in Quebec and convince westerners that the NDP is capable of "good public administration."
Much of the party is still "rooted in the past" and must zero in on the Prairies in much the same way NDP organizers focused on Quebec for the last six years, he said.
"We are not going to defeat Stephen Harper with a slogan," Mulcair said. "In Quebec, we united progressives from all parties, most of whom had never voted for the NDP before . . . Now we have to do the same across Canada."
Niki Ashton, who holds a seat in Manitoba, said Prime Minister Stephen Harper is taking westerners for granted. That will come back to haunt him and the Conservative party, she predicted.
The loss of western voters led to the virtual decimation of the Conservative party in 1993 and will do so again, she said.
"This is the beginning of the end of (Harper's) dominance in Western Canada," Ashton said. "Western Canadians don't support the kind of arrogance that we've seen in Ottawa."
Paul Dewar, who is supported by many of Manitoba's NDP strategists and cabinet ministers, said the province has elected provincial NDP governments for years and the federal party should build on that success.
"This is NDP country," Dewar said. "Clearly there is something going on here that we should take notice of."
Nathan Cullen said one way the party can attract more voters is by holding joint candidate meetings, but Dewar shot back by characterizing the idea as a "one-time offer" that sounded like a "ShamWow" commercial.
Cullen was undeterred, saying the idea is gaining traction among people who want to unite to end the current Conservative majority in Ottawa. The Conservatives have alienated people by ending the monopoly of the Canadian Wheat Board without consulting farmers and "ripping up our contract with the world on climate change," he said.
"The person making the greatest argument for this proposal is Stephen Harper himself," Cullen said.
Brian Topp said the NDP can't become another Liberal party because voters will just vote for the real thing if given the choice. He noted the NDP came second in the majority of western ridings last time, which he said lays the groundwork for the next election.
"Where we came second last time is typically where we won the following time," Topp said of previous elections. "We've got the bones of a pretty nice victory next time."
Toronto candidate Peggy Nash got applause for suggesting one of the ways the NDP could win some seats in western Canada is through electoral reform. Some 30 per cent of Saskatchewan voters cast a ballot for the NDP but that didn't translate into one seat, she said.
All party members are entitled to cast ballots starting March 1 via mail or the Internet, or at a leadership convention March 23-24 in Toronto.
Final membership numbers released Feb. 20 by the party show membership has swelled to 128,351, an increase of just over 50 per cent since the start of the leadership contest last October.
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