York—Simcoe
Provincial by-election in Ontario on September 3, 2026, after the departure of Caroline Mulroney (Progressive Conservative).
The PC Party is the favourite, with a better than 99% chance of winning and 55% of the projected vote.
Results
Connecting to the official count…
Preliminary results · Elections Ontario
The forecast
| Party | Projected share | Range (80%) | Chance of winning |
|---|---|---|---|
| Susan Lahey Progressive Conservative | 55.3% | | >99% |
| Naomi Davison Ontario Liberal | 25.2% | | <1% |
| Bobby Nikmard Ontario NDP | 9.7% | | <1% |
| Other | 5.4% | | <1% |
| Matt Pearce Ontario Green | 4.4% | | <1% |
Three points are stripped from the Progressive Conservative baseline — a deliberately small correction, since the evidence points to a structural lean and no pre-incumbency period exists to prove otherwise. No by-election turnout residual is applied.
What the forecast adjusts
- Personal vote removed
- 3 points removed from the Progressive Conservative vote: the share that went to Caroline Mulroney rather than to the party. 57.9% → 54.9%
The 2025 result
The race
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.
- Caroline Mulroney is vacating the seat she has held since 2018.
- Progressive Conservative share versus their province-wide score: +16.8 points (2018, her first election), +15.9 (2022), +16.4 (2025) — full from the start and flat thereafter.
- Redistribution leaves no pre-incumbency observation for this seat, so the correction stays cautious rather than assuming the premium is entirely structural.
- The Progressive Conservatives took 59.4% here in 2025 — the safest of the three Ontario contests. No candidates were named at the time of writing.