Associated Press: Chancellor Angela Merkel’s center-left rivals made it clear Monday they will make nuclear power a major issue in the September national election, following a weekend shutdown at a troubled German nuclear plant. The plant at Kruemmel, near Hamburg, shut down automatically on Saturday following a short-circuit in a transformer. The plant had reopened only last month after a two-year closure that followed a fire in another transformer in 2007. That offered the center-left Social …