Much better line of attack, but it's nothing particularly difficult to deal with. This isn't a subject Romney can use to much advantage, because in the end, at worst Obama is guilty of speaking too soon and then coming the the proper conclusion later, and disclosing that fact. That's not exactly a "there were no WMDs" type headache. It's a triviality or parsing statements.
"My administration has tried to keep the public apprised of our evolving understanding of the Benghazi terror attack, as best we could, with the information that we have had at hand. From the beginning, reliable sources indicated, and continue to indicate, that anger over the video may have contributed to the timing of the attack on the Libyan consulate, as it did, simultaneously, in Egypt. There were also initial, unsubstantiated indications that the attack might have been a preplanned act of terrorism. We needed to acquire firm evidence establishing that fact before making such an accusation. As the state department learned more, and hard evidence became available, we shared it with the public, as we will always do under my administration. I'll make no apologies for trying to keep the American people informed during such a tragic event, but take full responsibility for any inaccurate information that may have been given. As we learned more through a professional and thorough investigation, we came to understand that our initial assumptions were incomplete, and that our fears of a preplanned attack were accurate. The investigation is ongoing, and those responsible will be brought to justice. I have moved drones into the region with the full cooperation of the Libyan government. We will hunt down those responsible.
I can't know everything, but as President I will always try to keep the public as informed as possible on the issues that touch our lives. Sometimes, that may lead to information being distributed that turns out later to be inaccurate or incomplete, and we will admit as much, as we did here. But I'd much rather have a policy of open disclosure to the American people regarding foreign policy than the closed walls of the previous administration. Also, I killed bin Laden. Mittens straps his dog to the roof of his car."