Right,
"Mr President, why did you unilaterally declare war on Libya without the consent of congress?"
"Are you in fact aware that this contravenes the constitution of the United States to use the military to fuel your personal grudges?"
Considering that Romney was first for the war (criticizing Obama for not going far enough), then against (criticizing Obama for going too far) and then was for the war when it was over, it's probably not Obama that fears being asked about Libya. Also, after so many years of war propaganda in the US, being against successful wars is generally not a very popular position. Now, if someone would ask Obama: "Mr President, if the purpose of the intervention of Libya was to protect the civilians, why did so many civilians die during this operation?" that would be awkward, but such a question will almost certainly not be asked.
