Ontario Desk · By-elections
Three seats, three departures.
The three seats voted on September 3, 2026. Two were Progressive Conservative and one New Democratic, and all three were defended without the member who won them — one of them amid the hotel controversy that cost him his cabinet post. Official results are pending validation by Elections Ontario.
Called — September 3, 2026
The seat he built.
The Progressive Conservatives ran 11.7 points behind their provincial score here in 2018. Under Neil Lumsden — a former CFL player and Tiger-Cats executive — that deficit shrank to 0.9 points by 2025. He is gone, the party is carrying a scandal, and the Ontario Liberals now lead province-wide.
Favourite · Ontario Liberal 46 %
View forecast Scarborough-Sud-OuestThe fortress predates her.
Doly Begum resigned in February 2026 to run federally — for the Liberals — and won in April. It is tempting to read the New Democrat share here as hers. The record says otherwise: the seat ran more than 22 points ahead of the provincial NDP before she was ever on the ballot.
Favourite · Ontario NDP 76 %
View forecast York—SimcoeA name, not a margin.
Mulroney is the most recognisable name of the three departures, which makes the measurement more interesting: her premium did not grow. It was 16.8 points in her first election and 16.4 in her last. A margin that arrives fully formed belongs to the riding.
Favourite · Progressive Conservative > 99 %
View forecastNo by-election turnout residual is applied to these races. The only one Vote-Scope has measured comes from the April 2026 federal by-elections; transposing it to a provincial contest would be an assumption rather than a measurement.