Under the radar of most Canadians, New Democrats are in the midst of a fascinating decision about the face they put forward.

The leadership contest to replace Tom Mulcair won't result in a dramatic ideological shift for the federal third party. There is no Jeremy Corbyn-like figure offering a lurch toward hard-core old-school socialism; nor a left-wing equivalent to Maxime Bernier's near-miss campaign to get Tories to embrace a particular strain of modern conservatism. Policy disputes, among the five candidates, are fairly mild.

But in terms of whom they most naturally speak to and represent, what sort of voice they would provide, New Democrats will face some very distinct choices when they cast their ballots this fall.

Story continues below advertisement

Each contender – particularly Jagmeet Singh, Charlie Angus and Guy Caron, generally perceived by party insiders to have the best chances of winning – offers legitimate potential to open up a segment of the electorate. That means strategy-minded New Democrats have to weigh which constituencies they most want to cultivate, and which ones they are willing to risk alienating.

If New Democrats hope to crack into the suburban battlegrounds that go a long way toward deciding election outcomes – where, save for a fleeting breakthrough during the Orange Wave in 2011, they're usually an afterthought – Mr. Singh's allure is obvious.

The only New Democrat to have repeatedly been elected in the immigrant-heavy suburbs ringing Toronto, the 38-year-old deputy leader of the Ontario NDP has more to his formula than his unusual image as a turban-wearing Sikh who turns up in GQ fashion spreads and competes in mixed martial arts. Although currently running on broader national policies, such as heavily shifting the tax burden to the rich, Mr. Singh has proven adept during his provincial career at championing issues – from auto insurance to police carding – that resonate in ridings such as his Brampton one.

If that's one form of populism, Mr. Angus offers another. Although he has a substantive record of anti-poverty and First Nations advocacy, and is now campaigning on such policies as improving conditions for precarious workers, the Northern Ontario MP's appeal as a candidate is also tied up in how he presents himself. A sometimes silver-tongued former punk musician with blue-collar credentials, it's possible to envision him calling out Justin Trudeau in a way that resonates in places – other parts of northern or southwestern Ontario, say, or the Prairies – where New Democrats have historically had some success.

Then there's Mr. Caron, a more intellectual candidate who implicitly promises to keep the NDP viable in Quebec, where a decade of oft-mocked effort by Jack Layton culminated suddenly and shockingly in winning 59 seats in 2011.

Now down to 16 MPs there, still nearly half their total caucus, some New Democrats continue to see Quebec as the key to future competitiveness. Perhaps Mr. Caron, a former union economist running a policy-heavy campaign that includes a basic-income proposal, could restore gains from six years ago campaigning as a sunnier and fresher face than Mr. Mulcair was.

It is possible to look at this group and see opportunity even beyond a new leader building a new support base. Include northern Manitoba MP Niki Ashton – who rounds out the field with B.C.'s Peter Julian, and is trying to position herself as a feminist millennial voice for marginalized populations – and maybe there's a chance for the candidates to work together after one of them wins, jointly building a coalition of NDP-friendly demographics.

Story continues below advertisement

It's also possible to see the failure of some of these candidacies making it harder for the NDP to woo the constituencies they might have brought into the fold.

If Mr. Singh spends the campaign being treated as the front-runner and then loses to a middle-aged white guy, will his young, suburban supporters decide this isn't the party for them? If Mr. Caron builds momentum in Quebec but fails to get traction elsewhere, in a leadership campaign prompted by the humiliating ouster of another Quebecer, Mr. Mulcair, would potential backers in that province take it as a rejection of them as well? Would people who gravitated toward Mr. Angus's common-sense folksiness accept a bespoke-suit-wearing star of GQ spreads or a Quebec egghead speaking for them?

Runoff voting, in which party members will vote weekly until a candidate tops 50 per cent, might help build consensus. But unlike in the recent Conservative leadership when all ridings were weighted equally, the NDP's pure one-member, one-vote system could allow a candidate to overwhelm all the others by signing up lots of new members in a few ridings.

To the credit of Mr. Singh – who would probably have the greatest potential to do that, with high support in very democratically engaged Sikh communities – he instead appears to be running a truly national campaign, seeking support from all quarters.

That's a good reminder that neither he nor his competitors should be viewed just through the lens of their most obvious and immediate appeal. Whoever wins could very well prove able to reach far more broadly.

The ability to grow into the job in such a way is something party members should consider as they cast their ballots. But these would-be leaders wouldn't all be able to speak to the same voters, the same way, and that's something New Democrats will inescapably have to weigh as well.