Terrebonne in the 2025 Canadian federal election

As part of the 2025 Canadian federal election on April 28, 2025, an election took place for the federal electoral district of Terrebonne in Quebec. The competitive contest was primarily between incumbent Bloc MP Nathalie Sinclair-Desgagné and Liberal challenger Tatiana Auguste, together having received more than three-quarters of the votes cast. Following a judicial recount, Auguste was initially declared the winner with a single vote margin. Her election was upheld by the Quebec Superior Court in October 2025, but was overturned by the Supreme Court of Canada in February 2026, which voided the result. Auguste ultimately reclaimed the seat she was vacated from in the subsequent by-election held almost a year later.

The contest was made uniquely dramatic by a confluence of unusual factors, including the multiple changes to the outcome, the declaration of victor by a dramatic one-vote margin, and the proximity of the Liberal government to a majority. The intervention by the nation's top court further made it historically significant in a number of ways. The events following the contest were particularly tumultuous in an age where election outcomes are extremely rarely overturned and in a contest where no misconduct was alleged.

2025

• Election Night, April 28 - Preliminary election nights results had Liberal Auguste leading incumbent Bloc MP Sinclair-Desgagné by 35 votes; the governing Liberals led by Mark Carney gained over a dozen seats, placing the government within a few seats of majority
• Validation, May 1 - routine results "validation" put Sinclair-Desgagné in the lead by by 44 votes, reporting over 60,000 vote cast in total, including over 900 rejected ballots; the margin of victory triggered an automatic recount
• Judicial recount, week of May 5 - a judicial recount took place
• MP declared, May 10 - the judicial recount determined that Auguste received a single vote more than Sinclair-Desgagné, and consequently Auguste was declared elected; she was subsequently seated along with other newly elected MP, and spoke in the House of Commons for the first time on May 28
• Error reported, May 13 - it was reported that a voter intended to vote for Sinclair-Desgagné had her mail-in ballot returned to her due to a postal code misprint on the envelope provided by Elections Canada; Elections Canada later acknowledge that five other votes arrived late and were not counted due to the same error
• Election contested, May 23 - Sinclair-Desgagné filed court application to contest the election outcome
• Election upheld, October 27 - following hearing held the week prior, the Quebec Superior Court found that the printing error did not constitute an "irregularity" in election law, and rejected Sinclair-Desgagné's contested election application
• Leave to appeal granted, December 12 - The Supreme Court of Canada granted Sinclair-Desgagné a rare leave to appeal

2026

• Election Annulled, February 13 - shortly following oral argument, Chief Justice Wagner delivered the top count's decision to grant Sinclair-Desgagné's appeal; consequently Auguste's election in 2025 was voided and she was vacated from the seat
• Fresh election called, March 8 - By-election was called for Terrebonne and two electoral districts in Toronto
• By-election, April 13 - Auguste won by-election and regained the seat

On May 10, 2025, Auguste was declared elected as MP for Terrebonne at the conclusion of the judicial recount, with the following results.

The dramatic saga following the 2025 election contest in Terrebonne had two distinct phases - the recount and the contested election application. The outcome of the election was subject to scrutiny with entirely different focus in each phase. Judicial recounts, while uncommon, are conducted as a matter of course if the margin of victory is less than 1/1000 of the total votes cast. All events up to the conclusion of the judicial recount concerned solely with the proper counting and accurate tabulation of the ballots cast. No determination of other concerns relating to electoral irregularities would be dealt with in this phase.

The preliminary results reported immediately following the election, with all polls reported, had Auguste leading by thirty-five votes out of more than sixty-thousand cast. Election night results released by Elections Canada are the summations of the reported votes tallies of individual polls. The results are typically reported to the local returning officer by telephone.

As required by law, the local returning officer in Terrebonne conducted the result "validation" process in the presence of representatives of the candidates on May 1, 2025, during which the tally reports from all polls were examined for the purpose of correcting reporting and arithmetic errors. The law does not provides for examination of physical ballots during this process. The validation process netted no change to Auguste's and the NDP candidate's vote tallies, but shifted the numbers for Sinclair-Desgagné and for the candidates of the Conservative, People's and Green parties.

At the end of the validation process, Sinclair-Desgagné was in the lead by forty-four votes. The process also tallied the total vote cast to be over 60,000, and the rejected ballots to be over 900 in total. Given the margin of victory was less than 1/1000 of the total votes cast, an automatic recount to be overseen by a judge of the Superior Court of Quebec was triggered.

A recount of all ballots was ordered by Justice Danielle Turcotte of the Quebec Superior Court, and was conducted during the week of May 5. It was the first of four judicial recounts following the 2025 federal election to proceed. The recount increased the total number of valid ballots by seventy-four, with Auguste receiving the lion share of the gains. The various numerical changes from the recount resulted in Auguste being declared elected MP for Terrebonne by a single vote margin. Her election moved the Liberal seat count to 169, three short of a majority government.

The sensation single-vote victory certified by the judicial recount was soon subject to fresh attacks. The results became controversial after a would-be Bloc voter disclosed on May 13 that her mail-in ballot was rejected and returned to her due to a postal code misprint on the envelope provided by Elections Canada. On May 14, Elections Canada acknowledged the error but stated that it did not have legal standing to overturn the judicial recount. It further stated that five other mail ballots with the incorrect returning address printed had been rejected for having arrived at the Elections Canada office after the deadline; the statement said that they could not determine if the incorrect address had led to the fatal delay.

In September 2025, Elections Canada reported that 115 special ballots had been issued to electors in Terrebonne. Their disposition was as follows:

On May 15, Bloc Quebecois leader Yves-François Blanchet announced that the party would challenge the election result in court and seek a by-election. A application under the Contested Elections provisions of the Canada Elections Act was filed with the Quebec Superior Court in Sinclair-Desgagné's name on May 23, with the hearing scheduled in October. The application raised the gravity of the matter substantially by shifting the attack from votes being counted improperly to the election being conducted improperly.

The judicial hearing of the matter took place at the Saint-Jérôme courthouse starting on October 20. All parties forgoed calling live witnesses and instead filed affidavits for their record. The material filed by Elections Canada revealed that the special ballot officer of the electoral district estimated that 40 to 60 envelopes with incorrect return postal code was issued to voters but did not deem it necessary to inform the returning officer about the error, on the grounds that envelopes were being delivered by Canada Post despite the error, and that the return rate for special ballots was in line with previous elections. Counsel for Sinclair-Desgagné and the Bloc Quebecois seized upon the error, argued that it was sufficiently grave to meet the high threshold prescribed by the Supreme Court of Canada in a previous contested election case in 2012. Counsels for Auguste and the Liberal Party disputed the assertion, instead suggested that such error should be deemed merely as a minor one, noting that a single vote represented just a margin of 0.0016%. The advocate for Elections Canada stated that it recognized that an error had been committed in the election, but noted that the Supreme Court, while giving high priority to the right to vote, also said that Canadian elections were not designed to attain perfection.

The proceedings received press coverage not only in Canada, but also internationally, being reported in such outlets as CNN and The Guardian.

On October 27, the Superior Court of Quebec dismissed Sinclair-Desgagné's application to contest elections results. Justice Eric Dufour determined that the postal code error committed by Elections Canada was a human errors committed inadvertently and without any dishonest or malicious intent, and therefore in no way affects the integrity of the Canadian electoral system. Accordingly, he determined the error did not constitute an "irregularity" within the meaning of the Canada Elections Act, which would be required to contest the election outcome. Auguste's election victory was upheld accordingly.

On November 3, Sinclair-Desgagné announced that she would be appealing the ruling to the Supreme Court of Canada, and that she was also planning to set up a crowdfunding campaign to raise money for the litigation costs.

The Liberal Party subsequently filed a complaint with the Commissioner of Canada Elections, alleging that litigation costs form part of campaign expenses under the Canada Elections Act, and the anonymity given to crowdfunding donors violates the Act's limits on individual and corporate donations. Sinclair-Desgagné responded that she had received two legal opinions on the matter before proceeding with the initiative, and stated that the Liberal claim was "unfounded and malevolent". The federal commissioner then confirmed the legality of Sinclair-Desgagné's actions.

On December 12, the Supreme Court of Canada granted a rare leave for Sinclair-Desgagné to raise her appeal at the nation's top court. The full bench of court heard the matter on February 13, 2026, and on the same day Chief Justice Wagner delivered the court's decision to grant the appeal and to void the 2025 election results. Consequently Auguste was vacated from the seat with immediate effect, making her the first federal MP unseated by a court decision in 36 years. Written reasons for the decision were to be released at a later date. Elections Canada confirmed the announcement, and the Speaker of the House of Commons gave official notice of the vacancy on February 16.

Terrebonne's by-election was subsequently called for April 13, 2026, in conjunction with others to be held in Scarborough Southwest and University—Rosedale.

After reviewing its internal procedures, Elections Canada announced that, to avert the possibility of misdirected ballots in future, special ballots will no longer be manually prepared by a riding office, but will be centrally and automatically prepared at its Ottawa office.

While elections were frequently overturned in the 1800s, they have been extremely rare in modern times. The Supreme Court's reasons for its decision to vacate Auguste will likely prescribe further principles and guidelines that will be cited in many applications contesting elections for decades to come.

The top's court decision to vacate the seat was the first time the election of a MP was successfully overturned under the contested elections provisions in the Canada Elections Act since 2000 when those provision came into effect and replaced the previous Dominion Controverted Elections Act.

The unseating of Auguste was the first time a seated MP was vacated from their seat since the Supreme Court of Ontario ordered new election in 1989 for York North a seminal election dispute that saw not one but two individuals seated and then unseated, including Maurizio Bevilacqua who later served in cabinet and was until 2022 the mayor of Vaughan. That was the last instance where an election was overturned under the Dominion Controverted Elections Act before it was repealed in 2000.

The last instance when the nation's top court voided a federal election went back further and for conducts more clearly disreputable. In 1942 the Supreme Court unseated Liberal MP for Stanstead Robert Davidson for "corrupt practices", namely bribing voters with whisky and cash. That was also the only other instance where the Supreme Court overruled a lower court's determination of a federal election outcome. Its decision eight decades ago however led the matter down a more drawn-out path. The law in effect at the time put the determination of sanction in the hands of the House of Commons' Privileges and Elections Committee, which held off reporting its decision, and the subsequent byelection call, until May 1943, allowing Davidson to occupy for three years following the election in question. The ousted MP contested the byelection held August 9, 1943, but was defeated by the Bloc Populaire candidate Joseph-Armand Choquette.

Student votes are mock elections that run parallel to actual elections, in which students not of voting age participate. They are administered by Student Vote Canada. These are for educational purposes and do not count towards the results. The Liberals won in the poll.

• 2025 Terrebonne provincial by-election
• 2026 Terrebonne federal by-election
• 2025 Canadian federal election in Quebec
• Burnaby Central in the 2025 Canadian federal election
• Carleton in the 2025 Canadian federal election
• List of close election results