The Supreme Court of Canada (SCC) on Friday nullified the result of last spring federal election in the riding of Terrebonne, overturning a single-vote victory by Liberal candidate Tatiana Auguste due to an addressing error by Elections Canada. The SCC ruling leaves the Montreal-area seat vacant and sets the stage for a high-stakes by-election.

In the initial count, Bloc candidate Nathalie Sinclair-Desgagné had a lead of 44 votes, but a judicial recount took place under Canada’s election rules, which require a judicial review if the difference between the number of votes cast for the candidate with the most votes and the number of votes cast for any other candidate is less than one-thousandth (0.1%) of the valid votes cast. The recount flipped to the Liberals by a single vote, giving them 170 seats in the House of Commons.

Shortly after, a BQ supporter discovered her mail-in ballot was returned due to an addressing mistake made by Elections Canada. Sinclair-Desgagné then challenged the election outcome in court upon learning that the ballot was returned because of an error in the postal code printed on a label provided by Elections Canada, which they acknowledged. Although the Quebec Superior Court rejected Sinclair-Desgagné’s challenge, the Supreme Court of Canada reversed that decision.

In response to the ruling, Liberal Party spokesperson Matteo Rossi stated, “We respect the ruling and the institutions that underpin the strong trust Canadians place in the integrity of our democratic process.” Suzanne Proulx, President of the Bloc, also called for an immediate byelection, saying, “Now that the seat is vacant, we are demanding that the byelection be called without delay, so Terrebonne residents can go the polls rapidly.”