The caucus retreat is being held in Saskatchewan, the province many see as the birthplace of the party. Yet, the NDP has not held a seat in the province for almost a decade.
Mulcair blames the old "rurban" ridings, where the NDP's urban support was watered down in the "sort of pizza pie" design of the seats, which were weighted toward rural voters.
Now the ridings have been redrawn, two new urban ones have been created, and Mulcair is confident of success in two years.
"We're convinced we're going to be taking the majority of the seats in Saskatchewan in the next election," he said in an interview with CBC News.
Mulcair says the party has been busy building to the next election. "Whenever we're recruiting now, we're getting very strong candidates," he said.
And after ignoring the Liberal party for a year now, Mulcair has begun a two-pronged attack against both the Conservatives and the Liberals.
"We know that Canadians want change, and we know they're tired of being told something by the Liberals and then getting something completely different once they get elected," Mulcair said.
"They no longer want to believe that they have no alternative but to vote Liberal and Conservative in rotating fashion, and rotate in fact between Liberal corruption and Conservative corruption."
New ridings change voter makeup
If he hopes to win power, Mulcair must pick up new seats in provinces such as Saskatchewan, while holding on to those he already has, especially in Quebec.
Those 58 MPs will likely face questions this week about their position on Quebec Premier Pauline Marois's plans to create a Charter of Values, which would ban religious symbols in the workplace.
But Mulcair says Marois has raised controversial issues in the past and then not followed up. Mulcair's advice is to be cautious because there are no specific details yet on the proposal.
"What we're telling people is take the time to read what's actually going to be there," he said. "If it goes against people's religious rights, the NDP will do what we've always done, which is to be there for them and stand up for them, and defend them."