Supreme Court explains why it invalidated Terrebonne results in 2025 federal election

The Supreme Court of Canada recently ruled to invalidate a federal Liberal candidate's narrow one-vote victory in the 2025 federal election, aiming to maintain public confidence in the electoral system. The court's decision ensures that a federal election cannot be determined by a recognized and easily rectifiable administrative error.

Liberal candidate Tatiana Auguste had been declared the winner in the Montreal-area riding of Terrebonne by just one vote over her Bloc Québécois opponent, Nathalie Sinclair-Desgagné, back in April 2025. The Bloc candidate appealed the election results and requested a fresh election after a Bloc supporter alleged that Auguste had attempted to vote via mail using a special ballot that was not counted.

Although a Superior Court judge denied Sinclair-Desgagné's request for a new election, the Supreme Court overturned that decision in a split ruling delivered from the bench in February. Justice Mahmud Jamal authored the majority opinion, arguing that an Elections Canada employee had been aware for weeks about a mistake that led to some voters receiving envelopes with incorrect postal codes, yet the agency failed to remedy the issue.

Ultimately, Auguste managed to secure a second term in the riding through a byelection held in April. This report by The Canadian Press was originally published on September 18, 2026.