No candidate should drop his campaign plan for an issue that is classified. Classified means he can’t get any inside information. He has no power.
Actually he gets classified briefings. However he doesn’t have the power to de-classify any of the information. Hence he’s rather in a spot on this subject. He likely knows a lot more than he is allowed to say.
In addition, Romney will likely have to deal with this in an official capacity in the very near future.
During a time of war, keeping a closed mouth is wise.