CALGARY -- Tom Mulcair plans to maintain a low profile in Calgary for the next two days as he runs through mock exercises for Thursday's economic debate, which comes with very high stakes for the NDP leader.

His main goal of the campaign has been to sell the NDP brand as a credible alternative to replace Stephen Harper's Conservatives. Mulcair knows he faces an uphill battle to sell his pitch to Canadians.

"I think that it is because of the fact that we've had 150 years of alternating between the Conservatives and Liberals," Mulcair said Monday evening at a stop in Cranbrook, B.C.

"So, the old boys club is saying, 'Well, who is this new kid on the block who thinks that they can aspire to actually forming a government?"'

As Mulcair prepares for the debate hosted by the Globe and Mail, the party is expected to release the costing of its platform Wednesday. Mulcair will be the first of the three major party leaders to do so, but it comes as he has been dogged for weeks by questions about how he will pay for his spending promises while maintaining his pledge to balance the books.

This week alone, Mulcair has handed out multi-billion dollar health proposals.

They include a $100-million mental-health innovation fund for children and youth that he announced Tuesday in Lethbridge, Alta.

Mulcair says the four-year fund would include $15 million a year for health-care providers and community mental health associations.

It would also include $10 million a year for research and information-sharing among health-care providers across the country.

Other new NDP health promises include a $40-million commitment for a national strategy on Alzheimer's disease and dementia, $500 million to build medical clinics and hire more health-care professionals and $1.8 billion to expand home care and palliative services.

Liberal Leader Justin Trudeau has taken aim at the NDP for its financial plan, suggesting that Mulcair will have to make cuts to stay out of the red.

Trudeau also continues to repeat an attack on Mulcair suggesting the NDP leader cannot be "Tommy Douglas on a Stephen Harper budget."

"I don't mind the pressure," Mulcair said.

"That's why we are rising to the occasion and we will be publishing our numbers prior to Thursday's debate and I call upon Justin Trudeau and Stephen Harper to do the same thing ... Canadians have a right to know how we are going to do this."

The location for Thursday's economic debate provides a challenging political backdrop for the leaders, who have been grappling with sliding crude prices and uncertainty in the markets.

Mulcair insists the people of Alberta are "looking for another option."

Voters flocked to support the provincial New Democrats and elect a majority government under Rachel Notley, ending four decades of Progressive Conservative governments.

The federal party has not had the same appeal.

In 2011, the NDP only claimed one seat in the riding of Edmonton Strathcona.

Mulcair said he "loves nothing more" than being told that something is a fortress for the other parties.

"I remember in 2007 people thought I was foolhardy running in the Liberal fortress of Outremont in Quebec and we took it ... I've been elected there three times now," Mulcair said.

"Watch us go, people want change."