Whatever the outcome of this weekend's vote on Tom Mulcair's leadership, it's already apparent that the NDP is a party deeply divided — not just over whether he deserves to stay in the job, but over where the party needs to go.

One can't be separated from the other.

Mulcair, as we already know, led the New Democrats to a devastating result in the 2015 election. The party lost votes, over half its seats and its status as the Official Opposition in the House of Commons.

Worse still, the Liberals vaulted over the NDP in large part because Justin Trudeau out-performed Mulcair during the campaign.

But there's a growing sense inside the party that the Liberals really usurped the NDP as the party of choice among progressive voters, with the most obvious example being Trudeau's willingness to run deficits to invest in infrastructure, indigenous communities and health care.

Will Mulcair still be the leader of the NDP on Monday? Here's what could happen at the convention. 1:44

Heading into the weekend, the list of those who want a change at the top includes the party's youth wing, its socialist caucus and the president of the Canadian Labour Congress.

In a letter released this week, the youth wing urged NDP members to support "a new direction and new style of leadership."

It complains that young New Democrats were forced in the last campaign to argue against legalization of marijuana, against Mulcair's participation in a debate on women's issues and, well, on a host of other issues that ran counter to what young people believe.

A more progressive approach

For those who want Mulcair out as leader, the arguments amount to something like this: They want someone who's more progressive. More hip. More engaging. They see Mulcair as too top-down in his approach, a leader unwilling to listen or compromise.

In an interview with CBC's Peter Mansbridge on Wednesday, Mulcair went out of his way to signal a willingness to listen to grassroots members — even on proposals to keep fossil fuels in the ground to fight climate change, a contentious idea in Alberta, the province hosting this weekend's convention.

CLC president Hassan Yussuff on why he thinks the NDP needs a new leader 11:15

On the other side are some of the country's largest public and private sector unions, among them the Canadian Union of Public Employees and the United Steelworkers, who insist Mulcair remains the right person to lead the party. They see him as bright, experienced, principled and tough.

"I see Tom as a real fighter," CUPE's national president, Mark Hancock, said this week on the podcast edition of CBC Radio's The House. "He's a scrapper. He's somebody I want to have in my corner if I'm going into a dispute."

Somewhere in the middle is Mulcair's own caucus. There's no open rebellion, but neither are his MPs doing much to openly line up behind him.

It's an uncomfortable spot for a political leader who has spent the past few months accepting blame for the NDP's poor showing in the last campaign, and appealing for a second chance.

Under the party's constitution, Mulcair only needs the support of 50 per cent plus one of the 1,500 delegates expected in Edmonton this weekend to stave off a leadership race.

Mulcair says that's clearly not enough. And there, at least, he's getting no blowback.

The numbers game

Party president Rebecca Blaikie has mused that Mulcair probably needs 70 per cent, a figure others in the party insist is the minimum for Mulcair to claim the "moral authority" to stay.

And even then it could be a compromise of sorts. Some New Democrats quietly say they don't believe Mulcair can lead the party into the next election, but they don't want him to leave quite yet, when there's no obvious successor.

Either way, it's uncharted territory for a party with no history of deposing its leaders.

And if you're a Mulcair backer there's an added cause for concern. Nearly twice as many delegates as expected registered for this weekend's convention. It's unlikely, say party insiders, that the greater than expected turnout is among New Democrats interested in maintaining the status quo.

Looking for signs

With that in mind, here are some things to watch for this weekend in Edmonton as a gauge of how Sunday's leadership review might go:

How many speakers at the microphones focus on the past election's failures as opposed to focus on where the party needs to go? A collective inability to stop rehashing the 2015 campaign would indicate Mulcair has failed to convince members he can lead the party forward. How many will defend him? Many insiders are looking at the resolutions in Section 7 dealing with internal party democracy. If people really want to vent against Mulcair, that's where they'll do it.

How hard will delegates push the convention to adopt the so-called Leap Manifesto as party policy? The document drafted by activist writers Naomi Klein and Avi Lewis calls for the rejection of all new pipelines and fracking, the scrapping of trade deals and a focus on "localized, ecologically based agriculture" as part of a drive to an economy that will rely exclusively on renewable energy.

Discussions were underway before the convention to bring forward a resolution that would have the party endorse the principles of the manifesto with a commitment to work on ways to incorporate some — but not all — of the proposals as party policy. Mulcair is part of those discussions. How delegates who are demanding a more progressive agenda react to what's agreed upon will be another gauge.

What will Mulcair say in his speech to delegates? What tone will he strike on Sunday morning immediately before voting begins on the leadership review? A common view is that it's now up to Mulcair "to seal the deal" on his leadership. Everyone knows what happened in 2015. The goal in that speech has to be to convince people that he's the right choice to lead the NDP forward.

"He has to show he can raise money, bring in new members and identify those progressive issues that will distinguish the NDP under Tom Mulcair from the Liberals under Justin Trudeau,'' says one insider.

Mulcair's supporters argue a willingness to run deficits is no measure of how progressive your policies are. They say the NDP remains the only party that would scrap the Conservatives' anti-terrorism law. It's the only party opposed to a military role in Iraq. And the only party with a plan to tax corporations more heavily, or to propose universal, $15-a-day child care.

NDP National Director Karl Belanger explains what to expect from the NDP's convention in Edmonton. 6:05

It's no easy task. The sting of 2015 remains sharp. Rebuilding for a future four years away is still too distant.

As the British historian Lord Acton famously observed, "The long term versus the short term argument is the one used by losers."

It may well be the best argument Mulcair has, as he tries to hold on to his job, and to keep his party from the kind of divisive public quarrelling that eventually doomed the Liberals to the opposition benches a decade ago.