After disastrous elections for Labour in England, Scotland and Wales last week, the mood in Britain’s governing party is so rebellious that calls are growing for Prime Minister Keir Starmer to resign. Mr. Starmer, who won a landslide victory in 2024, has not only rejected that idea from some in his party, but, in an interview with The Observer newspaper, also suggested he could stay in power for 10 years. But one Labour lawmaker and former minister, Catherine West, has called on the cabinet to mount a putsch against the prime minister, warning that, if it fails to do so,...