**Andy Burnham stands as Labour’s candidate in the Makerfield by-election scheduled for 18 June 2026, following the resignation of the previous MP Josh Simons to create a route back to Westminster for the Greater Manchester mayor.** Traders assign an 88% probability that Burnham becomes an MP by 30 June because the constituency has long been a Labour stronghold, and recent polling and campaign reporting indicate he is the clear frontrunner despite a competitive challenge from Reform UK. A victory on 18 June would deliver the seat immediately, triggering his automatic disqualification from the mayoralty under rules governing combined-authority mayors who also serve as police and crime commissioners. No other parliamentary vacancy or procedural route appears viable within the tight timeline, so the market price largely tracks the implied probability of a Burnham win in this high-profile contest, which also positions him to pursue the Labour leadership.