Ayatollah Ali Khamenei orders a high-level clerical panel to investigate. All three of Ahmadinejad's challengers have alleged irregularities. TEHRAN, Iran — Iran's supreme leader today ordered an investigation into allegations of election fraud, marking a stunning turnaround by the country's most powerful figure and offering hope to opposition forces who have waged street clashes to protest the reelection of President Mahmoud Ahmadinejad.