Britain’s government is collapsing, and Prime Minister Keir Starmer’s possible resignation tomorrow is likely just the beginning. Starmer was already in trouble before Andy Burnham, the Labour mayor of Greater Manchester, won a by-election on Thursday that cleared his path to becoming Starmer’s replacement. Also damaging to Starmer were Labour defeats in May elections when the party lost more than 1,300 council seats while Nigel Farage’s right-wing populist Reform UK party gained more than 1,...