The York—Simcoe provincial by-election, scheduled for September 3 following Caroline Mulroney’s June resignation, features Susan Lahey as the Progressive Conservative nominee. Traders assign her a commanding 97.7% implied probability, reflecting the riding’s consistent PC support, Lahey’s profile as an East Gwillimbury councillor and local business owner, and Premier Doug Ford’s direct endorsement. Opposition candidates from the Liberals, NDP, Greens, and smaller parties remain fragmented with minimal polling traction. Factors that could realistically shift outcomes include unusually low turnout, late-breaking local controversies, or coordinated opposition consolidation, though historical patterns and current campaign dynamics favor continuity for the PC candidate.