Stacy Garrity's 94% implied probability as the Pennsylvania Republican gubernatorial primary frontrunner stems from her status as the sole ballot candidate following the March 10 filing deadline, bolstered by the Pennsylvania Republican Party's early endorsement and Donald Trump's January 2026 backing, alongside support from U.S. senators, representatives, and state leaders. Potential rivals like Doug Mastriano declined to run in January, though supporters launched a grassroots write-in campaign in early April without his endorsement, while John Ventre withdrew in February to seek lieutenant governor. With the May 19 primary approaching, trader consensus reflects her presumptive nominee position, though a surprise Mastriano write-in surge or late-breaking scandal could shift odds.