Liberals and Bloc Québécois both have a lot riding on Terrebonne by-election

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That the riding of Terrebonne is at all competitive tells you a lot about Quebec’s shifting political landscape in the Mark Carney era.

Until last year, the suburban riding on Montreal’s Rive-Nord had been a Bloc Québécois stronghold for three decades, with the exception of a one-term flirtation with the New Democratic Party in the ephemeral Orange Wave of 2011. But changing demographics, and Mr. Carney’s je-ne-sais-quoi popularity in Quebec, made the Liberals a contender in Terrebonne in 2025.

It took a judicial recount to crown Liberal Tatiana Auguste as the winner against Terrebonne’s then Bloc incumbent MP, Nathalie Sinclair-Desgagné, by a single vote. The Supreme Court of Canada annulled the election in February, after a postal-code error by Elections Canada on mailed-in ballots prevented at least one Bloc vote from being counted.

Now, Ms. Auguste and Ms. Sinclair-Desgagné are teed up for a rematch in an April 13 by-election that the whole country seems to be watching. The outcome will likely determine whether the Liberals secure the extra seat they need to form a clear majority government.

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A technical majority of 172 seats appears assured with Nunavut NDP MP Lori Idlout’s floor-crossing and expected April 13 by-election wins in the Toronto ridings of University-Rosedale and Scarborough Southwest. However, a victory in Terrebonne would give the Liberals a cushion without Speaker Francis Scarpaleggia needing to exercise his tie-breaking vote.

If that alone makes the by-election race in Terrebonne unusually interesting, the riding’s fast-changing demographics could also make it a harbinger of tougher days ahead for the Bloc and its sovereigntist cousin, the Parti Québécois, in the suburban ring around Montreal. The solidly francophone region, referred to as “le 450” owing to its area code, once reliably sent Bloc MPs to Ottawa. But the influx of first- and second-generation immigrants, many of them from arrival neighbourhoods in Montreal, has altered its ethnic profile.

Two decades ago, immigrants accounted for barely 2 per cent of the City of Terrebonne’s population. By 2021, that figure had risen to 12.6 per cent; the proportion likely hovers well above that now. What’s more, it does not include Canadian-born citizens of Haitian and North African origin who have left Montreal for Terrebonne and other suburban ridings in recent years.

The Haitian-born Ms. Auguste, who grew up in Montreal’s hard-scrabble Montréal-Nord borough, served as an aide to that neighbourhood’s Liberal MP before becoming a candidate in Terrebonne in 2025. She can likely count on solid support – and turn-out – among the riding’s voters of Haitian descent again now.

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Then there is Mr. Carney’s intriguing, and apparently growing, appeal in Quebec, where his government’s approval rating is slightly higher than nationally. The latest Léger poll, released last week, pegs Liberal support in Quebec at 48 per cent, an increase of more than five percentage points since the 2025 election. Support for the Bloc, meanwhile, has slipped to 25 per cent, down about 2.5 points from last year.

Mr. Carney’s much-panned January speech in Quebec City – in which he (mis)characterized the 1759 Battle of Plains of Abraham as a sort of kumbaya moment in Canadian history rather than the beginning of the end of New France as Quebeckers see it – has not left a dent in his popularity in the province. Nor has his curious lack of progress in French since becoming Prime Minister a year ago.

With wins in University-Rosedale and Scarborough Southwest likely in the bag, the Liberals have the luxury of pouring more resources into the Terrebonne race. Elections Canada rules enable political parties to pool resources nationally when multiple by-elections are held at the same time. That gives the Liberals a huge advantage over the Bloc in Terrebonne.

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“[T]he Liberals have little need to allocate resources to the two safe Toronto contests and can concentrate virtually all of [their] allowable national spending in Terrebonne,” 2021 Conservative campaign manager Fred DeLorey noted in a Substack post last month. “In a riding decided by one vote, that matters.”

The Bloc is hoping that fears about U.S. President Donald Trump’s trade war that drove some of its traditional supporters to Mr. Carney’s Liberals last year will have subsided enough to lure them back to the party. Bloc Leader Yves-François Blanchet and Ms. Sinclair-Desgagné insist the by-election is not about choosing a prime minister – Mr. Carney is comfortably in the job – but about ensuring a strong voice for Quebec in Ottawa.

That is a harder sell than it used to be in suburban ridings around Montreal. In Terrebonne, the Bloc is fighting for more than a just a seat in the House of Commons. Its very raison d’être may be on the line.