Andy Burnham holds a strong lead in the Makerfield by-election market due to his profile as Greater Manchester Mayor, local roots in the constituency, and Labour Party backing after Josh Simons resigned in May 2026 to create a parliamentary seat for him. This positions Burnham to challenge Keir Starmer for the Labour leadership if elected. Recent polls, including Opinium surveys, show Burnham ahead of Reform UK's Robert Kenyon by around five points among likely voters, though the race remains competitive in a seat where Reform placed second in 2024. Minor candidates from Restore Britain, Conservatives, and others trail far behind, with limited vote-splitting impact. The June 18 vote timing and national attention on the leadership implications reinforce trader consensus around Burnham's frontrunner status.