The Montreal MP met Sunday with his 101 caucus colleagues and the party's federal council, setting out immediately to heal the wounds from the bruising seven-month leadership contest.
"Together, united, we're going to face our only adversary, Stephen Harper's Conservatives, starting tomorrow!" he told pumped New Democrat MPs as they chanted his first name.
Mulcair moved swiftly to put to rest suspicions that he'd punish colleagues who supported rival candidates, clean house at party headquarters and sideline members of Layton's inner circle — most of whom had backed Mulcair's main rival, veteran backroom strategist Brian Topp.
Vancouver MP Libby Davies, a Topp supporter, will remain a deputy leader and Anne McGrath, one of Layton's closest confidants, will stay on as chief of staff through a transition period.
And he said he'll be keeping "98 per cent" of the party's existing management team.
Mulcair praised Topp's "extraordinary" work as one of Layton's campaign architects and said he looked forward to the benefit of his advice.
There was, however, one immediate casualty of Mulcair's ascension to the NDP throne: Brad Lavigne, who had served as Layton's principal secretary, national party director and national campaign director for the NDP's breakthrough election last May, immediately handed in his resignation.
It's an open secret in NDP circles that there is no love lost between Mulcair and Lavigne. However, Lavigne characterized his decision as simply moving on and said he decided months ago to make the break once a new leader was installed.
Mulcair triumphed over Topp after a long day of voting Saturday on four separate ballots. It was the culmination of a race that became increasingly nasty in the final few weeks, with the Topp camp accusing Mulcair of wanting to turn the NDP into a pale imitation of the centrist Liberals and of being temperamentally unsuited to the team-building job of leader.
But it was all sweetness and light Sunday as Mulcair sought to reassure colleagues that he'll take some time putting his own stamp on the party.
He said he won't disrupt the parliamentary team as it prepares to respond to Thursday's crucial, cost-slashing federal budget. Over the Easter break, he'll make some adjustments as leadership rivals, who had to give up their critics' posts to run, are reintegrated back into the team.
"It's going to be a cascading transition, but under the sign of continuity," Mulcair — clad casually in a blazer, jeans and an open-collared shirt — told a news conference.
More significant changes will come at the end of the summer, he added.
"When we come back in the fall, that's when the real battle begins," Mulcair said.
"We're facing a government that's very tough, very well structured and we've got to do the same thing. We've got to structure an official Opposition that will bring the fight to them like they've never seen before."
New Democrat MPs, who gave Mulcair a hero's welcome when he strolled into the room, were pleased with the magnanimous signals he sent in the wake of his victory.
"I'm over the moon," said Edmonton MP Linda Duncan, who had supported rival candidate Paul Dewar.
"I'm not feeling any animosity from anybody coming out of this first caucus meeting. Zero."
Mulcair claimed 57.2 per cent of the vote in the final, head-to-head showdown with Topp on Saturday's fourth and final ballot.
Within seconds of the final results being announced, the Conservative party issued a derogatory missive calling Mulcair "an opportunist whose high-tax agenda, blind ambition and divisive personality would put Canadian families and their jobs at risk."
The Tories have successfully launched incessant attacks on past Liberal leaders, helping to define Stephane Dion and Michael Ignatieff before they got a chance to define themselves for Canadians.
The NDP is determined not to let the Tories do the same to their new leader. Party officials have set aside several million dollars for an ad campaign, to be launched as quickly as possible, to introduce Mulcair to Canadians on his own terms. Mulcair spent Sunday afternoon filming footage for those ads.
At the news conference, Mulcair was dismissive of what he termed the Tories' sophomoric bully tactics, predicting they will eventually backfire.
"They're now in their seventh year in power and I think at some point, the secondary school behaviour and that type of thing, a lot of Canadians get tired of it. If they can't debate on the issues and they have to go personal, you know, we'll let them continue with that. We've got a different approach."
Mulcair predicted that by the next election in 2015, Canadians will be faced with "a stark choice" between the Conservatives and the NDP. But he acknowledged that the party has some work to do to convince Canadians that New Democrats are capable of providing "good, competent, solid public administration."
"Sometimes people have hesitated on that account. They've always liked our ideas but sometimes they've hesitated."
He said the NDP's challenge is to reach out beyond the NDP's traditional base.
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