A blunder meant this voter’s ballot wasn’t counted – then her pick lost by one vote. Now the case is in court

If you ever thought your vote doesn’t make a difference, this might change your mind.

A three-day hearing is underway in Canada to decide whether a single vote that went uncounted because of an administrative error should overturn a result in April’s elections for the national legislature.

Liberal candidate Tatiana Auguste won the electoral district of Terrebonne, north of the city of Montreal, by just one vote, flipping a seat that had long been held by the Bloc Québécois, Canada’s Quebec separatist party.

The highly unusual one-vote victory brought Prime Minister Mark Carney’s ruling Liberal Party, with 169 seats in parliament, closer to the 172 seats it needed to form a…