Polls open today in Toronto byelection that's considered a crucial test for Trudeau

Voters go to the polls on Monday in the federal riding of Toronto-St. Paul's in a byelection some perceive as a referendum on Prime Minister Justin Trudeau and the Liberal government.

Toronto-St. Paul's is considered a Liberal stronghold — the midtown riding has been solidly held by the Liberals for more than 30 years. But national polls suggest the Liberals are facing some of their worst levels of support in more than eight years of power. An aggregate of polling shows Conservatives leading by double digits.

Former Liberal staffer Leslie Church is running to replace former Liberal MP and cabinet minister Carolyn Bennett, who retired from politics after representing the riding for 26 years. 

Church is up against Conservative candidate Don Stewart, a former Bay Street worker whose first foray into politics could be both dramatic and memorable if he flips the riding blue.

Many pollsters and pundits say a Conservative victory will put pressure on Trudeau to step down as Liberal leader. Even a Conservative loss — if marginal — could be problematic for him.

"If we do end up on Monday night with a two, three, four, five-point win for the Liberals, the Liberals will be happy to have a win, but that still means that the country is going toward a big majority government for [Conservative Leader] Pierre Poilievre," polls analyst Éric Grenier, who runs thewrit.ca, said in an interview on Rosemary Barton Live.

Toronto-St. Paul's is seen as one of the safest ridings in the country for the Liberals. Even in 2011, when the party suffered its worst-ever result and was reduced to third-party status in Parliament, the Liberals took the riding by more than eight points.

David Coletto, chair and CEO of Abacus Data, said he believes the Liberals need to win by 10 points or more to give Trudeau a credible path forward.

"I think then the prime minister can probably say, 'Look, we can come back from this. We can convince people, persuade people to vote Liberal,'" Coletto said on Rosemary Barton Live. "If it is much closer, then I think there's going to be a lot more doubt about whether he and the current team are able to achieve some of those things."

The revolving door of prominent Liberals in the riding underscores just how seriously the Liberals are taking this race. Trudeau and at least 13 of his cabinet ministers have campaigned there on behalf of Church ahead of Monday's vote.

"We are taking nothing for granted. The whole team is there with her ... and we're going to keep on working until the last minute," Deputy Prime Minister Chrystia Freeland said on Sunday.

Also on the ballot is NDP candidate Amrit Parhar, Christian Cullis for the Greens, People's Party of Canada candidate Dennis Wilson and a flood of candidates unaffiliated with any party.

Dozens of independents have entered the race as part of an organized protest against Canada's first-past-the-post voting system. A record 84 candidates are on the federal ballot, making it almost a metre long, according to Elections Canada. 

Already more than 10,000 ballots have been cast during the four-day advance poll two weekends ago — an estimated 12.7 per cent of the riding's 84,668 registered voters.