Will Keir Starmer cease to be UK Prime Minister at any point in 2026?

This market asks whether Keir Starmer will cease to be UK Prime Minister at any point in 2026. Starmer's position remains in severe crisis following May 2026's disastrous local election results, which triggered at least five ministerial resignations including Health Secretary Wes Streeting, with nearly 100 Labour MPs now calling for his resignation. The critical gatekeeper is the Makerfield by-election on June 18, where Andy Burnham must win to enter Parliament and launch a formal leadership challenge (requiring 81 MP nominations). The first constituency poll shows Burnham at 43% and Reform UK at 40%—a tight race within the margin of error. External prediction markets closely align with the current quote at approximately 71.5% probability he leaves by year-end, suggesting the market sees the Makerfield result as the pivotal trigger. If Burnham wins and triggers a challenge, Starmer's departure becomes highly likely; if Burnham loses, Starmer's survival through 2026 becomes more plausible.