Andy Burnham leads the Makerfield by-election market at 73.5 percent as the Labour candidate, reflecting his established regional profile as Greater Manchester mayor and the party's decision to fast-track his selection after Josh Simons resigned the seat in mid-May to enable a parliamentary route for leadership ambitions. Reform UK's Robert Kenyon trails at 24.5 percent amid the party's recent local election gains in the constituency and national polling strength, though Burnham's personal vote and the short campaign window favor the frontrunner in trader assessments. Other candidates remain at minimal levels consistent with limited visibility. The June 18 vote remains the key upcoming event that could shift probabilities if turnout patterns or late developments alter the current positioning.