Montreal, Canada – A special parliamentary race is testing Justin Trudeau’s Liberal Party, as the Canadian prime minister faces weak polling numbers and simmering pressure to step down as party leader ahead of the next general election.

The vote on Monday — known as a by-election — will fill a vacant seat in Parliament to represent an electoral district in southwestern Montreal that has been a Liberal Party stronghold for years.

But recent surveys show a close fight between the Liberals, the Quebec nationalist Bloc Quebecois and the left-leaning New Democratic Party (NDP).

Experts say the vote will effectively be a “litmus test” for the Liberals ahead of the next election, which is set to take place before the end of October 2025 and appears likely to end nearly a decade of Liberal governments.

“It’s absolutely indispensable for the Liberals to hang onto this seat,” said Rick Bisaillon, a political science professor at Concordia University in Montreal.

The by-election in the electoral district (known in Canada as a riding) of Lasalle-Emard-Verdun comes at a tumultuous time in Canadian federal politics — and for the Trudeau-led Liberals in particular.

Campaign posters on a street in the Montreal neighbourhood of Ville-Emard ahead of the by-election [Jillian Kestler-D’Amours/Al Jazeera]

Parliament is set to resume on Monday — the same day as the vote in Montreal — and last week, the left-wing NDP abruptly announced its withdrawal from a 2022 agreement to prop up Trudeau’s minority government.

“Justin Trudeau has proven again and again he will always cave to corporate greed. The Liberals have let people down. They don’t deserve another chance,” NDP leader Jagmeet Singh said in a video announcing the decision on September 4.

The move means the Liberals are more vulnerable if a no-confidence vote is triggered in the House of Commons, and the result of that vote could force Trudeau to call an early election.

Meanwhile, the prime minister, who has been in power since 2015, has seen his popularity plummet amid soaring costs of living and a deepening housing crisis. Recent polls show Trudeau and his party far behind the opposition Conservative Party of Canada.

And that dwindling public support has spurred discontent from members of Trudeau’s own party, as well as former Liberal politicians.

In June, for instance, one Liberal MP called on Trudeau to step down as leader after the party lost a longtime seat in a widely watched Toronto by-election. Another MP recently told reporters that her constituents were “very adamant” that Trudeau is “no longer the right leader”.

Liberal staffers also said last month that they would not help the party campaign in the Montreal by-election in protest over the government’s pro-Israel policies amid the Gaza war, including arms transfers.

Against that backdrop, the stakes of the Montreal race “are unusually high”, explained Stewart Prest, a political science lecturer at the University of British Columbia.

Trudeau has said he plans to stay on as Liberal leader through the next election [Jennifer Gauthier/Reuters]

“If they are unable to hold onto this riding in the wake of that loss in Toronto, it gives fresh ammunition to those who are saying it’s time for a significant change in the Liberal Party,” Prest told Al Jazeera.

And that, he said, would “inevitably turn to the question of whether Justin Trudeau should continue to stay on as leader”.

‘A lot of dissatisfaction’

Just days before the vote in Montreal, Wellington Street — one of the main thoroughfares in the neighbourhood of Verdun — was lined with campaign posters for each of the main local candidates.

Residents have faced a deluge of campaign material over the past several weeks, and local and national media have covered the ins and outs of the race. Yet Trudeau’s face has been conspicuously absent from the local Liberal candidate’s signs — a reflection, to many observers, of his unpopularity.

“Right now, there’s a lot of dissatisfaction with Mr Trudeau’s government, and that’s probably going to be felt,” said Benoit Frenette, a Verdun resident who was out walking his dog on a quiet morning.

“I’m more of a nationalist at heart, so in that context, the Bloc Quebecois is an option I’m considering,” he told Al Jazeera.

A poll on Thursday found that the Bloc Quebecois candidate in Lasalle-Emard-Verdun had a lead over the Liberal and NDP candidates, while the Conservatives trailed far behind the pack.

A view of NDP candidate Craig Sauve’s campaign office on Wellington Street in Montreal, Canada, before the by-election [Jillian Kestler-D’Amours/Al Jazeera]

The Bloc’s Louis-Philippe Sauve had 29.6 percent support compared with 24.1 percent for the Liberals’ Laura Palestini and 23 percent for the NDP’s Craig Sauve, The Canadian Press news agency reported. Conservative candidate Louis Ialenti was at 7.3 percent.

Verdun residents Lauren Cinq-Mars and Megan Cott, both 24, said they planned to cast their ballots for the NDP, but neither was particularly enthusiastic.

“I feel very strongly against the Conservatives … and I feel like the Liberal Party has gone more centrist than I’m comfortable with,” Cinq-Mars told Al Jazeera.

“I think we know that we’re going to go Conservative the next [general] election, and I think Justin Trudeau should step down and let someone fresh motivate people because it’s not going to happen with him,” Cott added.

In the neighbouring Ville-Emard area, resident Ali Derauiche said housing and family values were among his main concerns. But he was still undecided over whether to vote for the NDP or Liberal candidate.

“It’s going to be close between the NDP and the Liberals,” Derauiche said of the upcoming vote, adding that while he personally wasn’t frustrated with Trudeau and his government, he could understand those who are.

“Political parties, that’s what it is. At a certain point, you make a change. You get used to someone, but at some point, you want to see other figures, other projects.”

Campaign pamphlets for the leading candidates in the Montreal by-election [Jillian Kestler-D’Amours/Al Jazeera]

A turning point?

So far, Trudeau, who attended a caucus retreat in British Columbia this week, has insisted that he will stay on as leader through the next election. “Ready for Parliament’s return next week,” he wrote in a social media post on Wednesday.

“Some parties are focused on playing politics. We’re focused on what really matters: saving Canadians money on groceries, medication, and the cost of their home — real economic relief.”

According to Bisaillon at Concordia University, Trudeau is unlikely to step down even if the Liberals lose in the Montreal by-election. “He seems almost convinced that he’s got a mission from God,” he told Al Jazeera.

Bisaillon said the race has highlighted “a desire for change and frustration” among Canadians that will be felt in the upcoming general election.

“It’s the ‘second big dog’ that’s going to win here,” he said of Monday’s vote. He noted that the Conservatives won the Toronto by-election in June because they were the most popular alternative to the Liberals.

“But the Conservatives in Quebec are not the second big dog; they’re like third or fourth down the line. The second big dog here is either Bloc or NDP.”

Prest at the University of British Columbia added that a Liberal loss on Monday could end up being a “turning point” for the party.

“Are they willing to continue to fight under this leader, or would you start to see stronger calls from within the party for a change in leadership?” he asked.

“It will be fascinating to watch — if the Liberals fail to keep the seat — if indeed the MPs are essentially jolted into action or if they continue to turn their attention elsewhere and the Liberals continue to seemingly coast towards the inevitable defeat” in the next election.