Hours after Canadians went to bed disappointed by a Stanley Cup loss Monday night, the Conservatives scored a stunning byelection upset to win in the longtime Liberal stronghold of Toronto-St. Paul鈥檚.

Conservative candidate Don Stewart eked out the win by just 590 votes over Liberal Leslie Church in an early morning upset, yanking away a riding the governing Liberals have held for more than 30 years.

Conservative Leader Pierre Poilievre demanded the prime minister call a snap election after what he described as a 鈥渟hocking upset鈥� on social media Tuesday morning.

鈥淗ere is the verdict: Trudeau can鈥檛 go on like this. He must call a carbon tax election now,鈥� Poilievre said on X.

Stewart trailed Church for hours overnight as poll workers slowly counted ballots that were stacked with independent candidates, thanks to a protest group trying to make a point about the first-past-the-post system.

Stewart tried to sound upbeat when he visited his campaign office at around 11:30 p.m., but he didn鈥檛 quite succeed as the polls showed his opponent in a steady lead.

鈥淟et鈥檚 not give it up,鈥� he said.

Both Stewart and Church had closed up their campaign parties hours before the final results, when it became clear the vote count was going to extend into the early morning hours.

The results flipped just before 4 a.m. when Tories jumped into the lead with just three polls left to be counted.

The results represent a massive victory for Pierre Poilievre and his Conservatives, who haven鈥檛 won a single seat in Toronto proper since 2011.

Church said she plans to run again as the Liberal candidate in the next general election.

鈥淵esterday voters in Toronto-St. Paul鈥檚 sent us a clear message, that they want us to re-earn their trust,鈥� Church said in a statement posted to X Tuesday morning.

鈥淭hey want a government that fulfils its promise to be there for them.鈥�

The race was considered a must-win for Prime Minister Justin Trudeau, and the loss is a massive blow that could trigger calls for him to step down after 11 years as Liberal leader.

The crushing defeat for the Liberals is a kick to a party that is already down in the polls. The vote proves the polls reflect reality, said Scott Reid, who worked as the director of communications for former prime minister Paul Martin.

鈥淚 don鈥檛 think it鈥檚 possible to overstate how consequential this byelection loss is,鈥� said Reid, who woke to the news Tuesday morning.

鈥淚ts implications could be vast for the government, for the prime minister, for the timing of the next election. I mean, this is a Yahtzee.鈥�

Typically, when Conservatives do well in urban ridings, it鈥檚 because the New Democrats have siphoned off support from left-wing voters, said Ginny Roth, a Conservative strategist who served as Poilievre鈥檚 director of communications during his leadership race.

That wasn鈥檛 true for Monday鈥檚 byelection, when the Liberals and Conservatives went head-to-head and the NDP candidate garnered only 11 per cent of the votes.

But if the same holds true for other seats across the country, it could change the strategic dynamics of the next election, Roth said Tuesday.

鈥淚t鈥檚 a really buoyant, exciting prospect for Conservatives who, I think, now can point to a very broad coalition of support,鈥� she said.

The contest was Stewart鈥檚 first election. The financial executive has close ties to the Conservative party as a longtime organizer and a former colleague of Jenni Byrne, an informal Poilievre adviser.

Toronto-St. Paul鈥檚, in the city鈥檚 midtown area, includes some of Toronto鈥檚 wealthiest addresses as well as an above-average number of renters, and one of the largest concentrations of Jewish voters in the country.

Carolyn Bennett, the former Liberal cabinet minister whose resignation in January triggered this byelection, won the seat nine times for the Liberals, and by more than 20 percentage points every time except once.

But the Liberal campaign was challenged by a cranky electorate that lost patience with Trudeau amid soaring inflation, unaffordable housing and a rise in hate crimes since the start of the Israel-Hamas war.

Conservatives appealed to the riding鈥檚 Jewish community during the race, urging them to vote for the Tory candidate to send a message to Trudeau about what they describe as silence in the face of a rise in antisemitism.