British Prime Minister Keir Starmer, reeling from a crushing local election defeat, faced a new setback to his leadership on Saturday when a former minister said she would challenge him for the top job if no one else stepped forward. Starmer’s Labour Party recorded the worst losses of a governing party in municipal polls since 1995, prompting a growing number of his own lawmakers to call on him to quit. To try to shore up his position in the party earlier on Saturday, he named two influential...