Editor's note: Peter Bergen, CNN's national security analyst, is a director at the New America Foundation and the author of the new book, "Manhunt: The Ten-Year Search for Bin Laden -- From 9/11 to Abbottabad." (CNN) -- On Monday, Republican presidential candidate Mitt Romney called for the appointment of a special prosecutor to investigate a series of recent leaks that critics charge are designed to bolster the national security credentials of the Obama administration. Investigations by special prosecutors can take on a life of their own. Recall that the investigation of the Whitewater real estate deal in Arkansas -- in...