An Ecuadorian presidential candidate known for speaking up against corruption was shot and killed Wednesday at a political rally in the capital amid a wave of startling violence in the South American country. President Guillermo Lasso confirmed the assassination of Fernando Villavicencio and suggested organized crime was behind his slaying, less than two weeks before the Aug. 20 presidential election. “I assure you that this crime will not go unpunished,” Lasso said in a statement.