Susan Lahey holds a commanding position in the York—Simcoe provincial by-election market as the Progressive Conservative candidate in a riding the party has held continuously since its creation. The seat became vacant following Caroline Mulroney’s resignation in June 2026, prompting Premier Doug Ford to appoint Lahey, an East Gwillimbury councillor and small-business owner with local community ties. The PCs captured 59 percent of the vote in the 2025 general election here, and Lahey faces a divided field of seven candidates including Liberal Naomi Davison and representatives from the NDP, Green, New Blue, Libertarian, and Ontario parties. Nominations closed on August 20 ahead of the September 3 vote, with advance polls scheduled for late August. Trader consensus reflects the riding’s consistent PC margins and limited opposition visibility, though any late campaign disruption could still shift dynamics before election day.