Why a by-election in northwest England could decide Keir Starmer's future

Britain holds a crucial by-election today. The vote could trigger a leadership challenge against Labour's Keir Starmer. Andy Burnham, a popular mayor, aims to win the seat to run for party leader. If he wins, Starmer's position becomes precarious. The outcome rests with voters in the Makerfield constituency. A result is expected early Friday.