More than half of Canada's New Democratic Party (NDP) voted to launch a new leadership race and ditch Thomas Mulcair.

The convention marks the party's intention to tack leftwards, eschewing Mulcair's strategy of trying to bring the party to the political center.

In advance of the vote on his political future, Mulcair delivered a last-ditch effort to stay — an impassioned, albeit familiar, speech to party faithful on Sunday morning, peppered with stock leftist phrases like 'big banks' and 'creeping privatization' with some beatification of former party leaders. It ultimately proved unsuccessful, as 52 percent of the delegates at the convention in Alberta's capital voted to launch a new leadership race to replace Mulcair.

The results were announced in French and were met largely by stunned silence, as it took a few seconds for delegates to process the results. Even minutes later, the crowd seemed to remain slightly shocked, with delegates quietly talking with each other, largely ignoring the continued goings-on at the convention.

The results appeared to catch even Mulcair himself off-guard, as he delivered a largely improvised speech accepting the results after they were delivered. "Don't let this very divided vote divide us," he told members.

That leadership race will likely be a fight over the party's core philosophy, as the party contemplates styling itself more after avowed leftists like American Democratic primary candidate Bernie Sanders or U.K. Labour Party leader Jeremy Corbyn, as opposed to emulating a more third-way labour party.

Mulcair, who was elected as leader in 2012, agreed to stay on as leader until a successor is chosen.

The surprising results came after the NDP's disastrous result last October, turning a five-point lead into a humiliating third-place result — shedding 51 seats in the House of Commons, and dropping 10 percent in the popular vote over its previous election result, which had been the party's best-ever showing.

Mulcair's penance for the party's drubbing in the last election was largely lacking, and the membership appeared to pick up on that.

"I share your deep disappointment in the election results," Mulcair told the convention floor near the beginning of his Sunday morning speech, but proceeded to laud his party's performance during the campaign, and double-down on many of its core policy positions that had been put forward during the election, including rejecting the Trans-Pacific Partnership (TPP), overhauling the electoral system, instating a $15-an-hour minimum wage for federally-regulated workplaces, and implementing a national childcare program.

Many in the party began to suspect that the NDP, once an avowed socialist organization, had lost support to Justin Trudeau over the course of the campaign by being out-flanked on the left by the traditionally-centrist Liberal Party.

The party, during the campaign, refused to endorse hiking personal income taxes on the top one-percent, wouldn't commit to legalizing marijuana, and ruled out any deficit spending, even if that meant cuts to federal programs — three things that Trudeau's Liberals explicitly supported.

That concern, that the party had sacrificed principle for power — and wound up with neither — is what put such focus on Mulcair's speech in advance of the vote.

It also served as a direct ask, from Mulcair to the party members, to keep him in the job.

The leadership vote is usually just a perfunctory agenda item that has, in the past, resulted in more than 90 percent of the delegates voting to endorse the existing leader.

This time, however, Mulcair was forced to campaign aggressively to receive the party's backing. Under the party's rules, if less than half the party membership votes to support Mulcair, a leadership review is triggered, which would likely result in a fresh leadership campaign.

This is the first time in Canadian history that a party turfed their leader at a party convention since 1967*.

A foreshadowing for the leadership review was the debate and vote around the Leap Manifesto — a document calling on the party to commit to "energy democracy" and, more specifically, to completely eliminate the use of fossil fuels by 2050. It further demands an "end to all trade deals," new taxes on the financial sector, an end to pipeline construction, cuts to military spending, a guaranteed minimum income, and an end to austerity.

A resolution at the convention that effectively endorsed the Leap Manifesto — adopting it as a "high-level statement of principles" — carried with a clear majority. And while it doesn't call for the wholesale adoption of the document per se, it does call on the party to debate the manifesto on the local level, and to bring back its core tenants at the party's next policy convention in 2018.

The side stumping for the manifesto included a litany of former Members of Parliament for the party, including Megan Leslie, defeated in her riding of Halifax, and Libby Davies, the former deputy-leader of the party who thundered that "this party has a long and proud history for standing up on the right side of history," amid raucous applause, comparing the manifesto to her party's opposition to Japanese internment camps during the World War II.

Avi Lewis, a key proponent of the document along with his wife Naomi Klein, opened the debate and emphasized that approving the resolution just meant the start of the discussion: "Don't let this debate be the end. Let it be the beginning."

"Please, do not hang a millstone around the neck of our leader here in Alberta," said Alberta Federation of Labour president Gil McGowan, who was the party's candidate in downtown Edmonton.

The party's possible endorsement of the document led to criticism from members of the Alberta NDP — which won government last year in oil-rich and staunchly conservative Alberta — with Premier Rachel Notley overtly supporting the approval and construction of a new oil pipeline in her well-received speech on Saturday.

Shannon Phillips, the province's environment minister, described support for the document as "ungenerous, short-sighted and ... a betrayal of the people who voted NDP in this province last year."

Shortly after the motion on the Leap Manifesto was adopted, Alberta's opposition leader came out swinging.

"I am very disappointed in the radical anti-Alberta resolution that was passed today by the federal NDP," Brian Jean, leader of the right-wing Wildrose Party, said in a statement.

The adoption of the resolution is an unequivocal break from the party's position that it brought into the 2015 federal election, and may be a clear sign that the party is looking to move aggressively to the left in the short-term.

*Correction: An earlier version of this story said that Mulcair's ousting was the first of its kind. In fact, a 1967 convention forced a leadership race, pushing their leader, John Diefenbaker to defend his job. He ultimately failed to do so and was replaced with Robert Stanfield.