The United Kingdom has seen remarkable churn at the highest level of government, going through six prime ministers in the last 10 years, largely due to turmoil within the Conservative Party. Now Keir Starmer, the leader of the Labour Party and U.K. prime minister since 2024, could be headed for the exits as well, thanks to a storm of scandal, procedure, and politics. What is the controversy? Why We Wrote This Less than two years since becoming British prime minister, Keir Starmer is fighting to keep his job. Mr. Starmer’s appointment of Peter Mandelson as U.K. ambassador in Washington is at the heart of the political scandal. The root of the issue is the appointment of Peter Mandelson, a longtime Labour Party politician, as British ambassador to the United States in February 2025. Mr. Mandelson has had a history of controversy in his career, having twice resigned from government Cabinet positions over conflict-of-interest concerns. The problem for Mr. Starmer is that when Mr.…