The federal NDP, these days, is throwing everything it has to get its leader, Jagmeet Singh, elected in a byelection in a riding in B.C. where the party has long had deep roots even as it appears to be all but conceding a byelection in the beachhead established by its former leader, Thomas Mulcair, in Quebec.

That a New Democrat, let alone its leader, should even be worried about succeeding in the riding of Burnaby South is a remarkable thing. The last time voters in at least parts of Burnaby were not represented by a New Democrat in the House of Commons was 1968.

A win in Burnaby South for the NDP leader is, no doubt, important. But the pending loss of the Montreal riding of Outremont may be far more important, not just a symbol of NDP weakness but also the beginning of the mopping up of the last drops of the Orange Wave that swept across Quebec in 2011.

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Outremont is not, to be sure, a natural NDP riding. Among other things, it is one of the most affluent ridings in the country. And with one brief blip when Brian Mulroney’s PCs won it in 1988, it had been reliably Liberal stretching back at least to the 1930s — until Mulcair came along and, in a 2007 byelection, stole it from the Liberals.

That a Liberal stronghold could be stolen by a New Democrat — in Quebec, of all places! — turned out to be a harbinger of the Liberal Party’s decade of electoral darkness. The late Jean Lapierre, whose retirement as the Liberal MP for Outremont cleared the way for Mulcair, would quip during the 2011 election that the only red signs he could see in Quebec in that campaign were stop signs.

That election, of course, was the nadir of Liberal fortunes in Quebec and elsewhere, all heralded by its loss of Outremont.

Now it appears the return of Outremont to the Liberal fold may be a harbinger of the end of the NDP in Quebec. Jack Layton won 58 of Quebec’s 75 seats in 2011. Mulcair could hold only 16 in 2015. But that 16 was more than one-quarter of the entire NDP caucus. Now Singh — NDP, Liberal and Conservative insiders say — is in danger of losing all but one or two in the province.

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“All of the NDP seats are truly up for grabs,” said Carl Vallée, a partner in the Montreal-based consultancy Hatley Strategies and a former senior aide to Stephen Harper.

Karl Bélanger, who twice ran, unsuccessfully, for the NDP in the Lac-Saint-Jean region before spending more than a decade as a senior aide to leaders Layton, Mulcair, and Alexa McDonough, concedes that his party stands to lose the work of a generation in Quebec. “It will be very tough.”

And several Liberal MPs from Quebec, speaking on background over coffee at this week’s caucus meetings in Ottawa, shared the same assessment of NDP fortunes.

WATCH: Former BC Liberal MLA Richard Lee named as federal Liberals’ new candidate in Burnaby South

1:39 Former BC Liberal MLA Richard Lee named as federal Liberals’ new candidate in Burnaby South Former BC Liberal MLA Richard Lee named as federal Liberals’ new candidate in Burnaby South

The problem for the NDP is two-fold. First, the party, having only established itself in Quebec less than a decade ago, has not grown roots that are strong enough to withstand the second problem: the inability of its leader to connect in any meaningful way with Quebec voters. (One could argue that Singh has failed to connect with voters in the rest of Canada as well, but that thesis can be tested another day.)

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To the extent the NDP had success in the last two general elections, it is, arguably, because it became the preferred choice of the Not-Liberal vote in the ridings it won. There are several ridings, most, but not all, outside Montreal, where there is a significant part of the electorate that doesn’t, won’t, can’t vote Liberal.

But now there are new choices for that Not-Liberal vote. The Bloc Quebecois has a new leader, Yves-Francois Blanchet, who, even his party’s opponents say, is a good bet to stabilize that party and perhaps even grow its support a bit. All 10 BQ MPs are re-offering this fall even as some of the NDP’s biggest names in Quebec — Hélène Laverdière and Romeo Saganash, for example — will retire.

The BQ can expect to get increased consideration as the preferred anti-Liberal vote. Just a small shift from the NDP to the BQ could see the BQ steal some NDP seats. Salaberry—Suroit, in the province’s southwestern corner, is a good example. New Democrat Anne Minh-Thu Quach squeaked out a win with 30.4 per cent of the vote in 2015. The Liberals could only muster 29.2 per cent even while Trudeau was dominating the rest of the province while the BQ, running a former MP there, was right in the thick of it with 28.4 per cent.

WATCH: Andrew Scheer promising Quebec more autonomy over immigration

1:00 Andrew Scheer promising Quebec more autonomy over immigration Andrew Scheer promising Quebec more autonomy over immigration

Andrew Scheer’s Conservatives are also quietly hopeful of gains in Quebec this fall. His well-regarded provincial lieutenant, Alain Rayes, and his Quebec caucus have been building the case that they should receive consideration from those free-market, small government, nationalist voters that helped elect Francois Legault and the CAQ to government in Quebec City. The Conservatives hope to steal Rimouski and Jonquiere and perhaps others from the NDP.

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And yet, Trudeau’s Liberals could still be the biggest beneficiary of the NDP demise in Quebec.

In those ridings where, to put it crudely, the ballot choice comes down to Liberal or Not-Liberal, a weakened NDP, a stabilized Bloc, and a growing Conservative Party may not have established themselves as the dominant Not-Liberal choice. As a result, the Not-Liberal vote could splinter relatively evenly among those three parties and allow a Liberal candidate to win a first-past-the-post race with as little as 30 per cent of the popular vote.

Any Liberal gains in Quebec this fall will be crucial in offsetting expected Liberal losses elsewhere in the country and those Quebec wins — the result of a weakened NDP — could help sustain Trudeau’s majority.