Just the week before, he had loudly "spiked the football" again on killing Osama bin Laden. He had contended Al Qaeda was no longer operative as a result. This led to Egyptian protestors chanting "Obama! Obama! There are a thousand Osamas!" - but the MSM really didn't want you to hear about that. When Benghazi happened and it immediately became clear it was an organized terrorist action, Obama felt immediately he could not act to stop it without losing face. And "face" is everything to people with his type of background. They decided to try to use the minor protests going on in Egypt over the YouTube video being show on Egyptian TV as a cover story for what happened in Benghazi.
The takeaway is - Obama (or Valerie Jarrett) thought using military force to stop an Al Qaeda attack would be more politically damaging to his campaign than doing nothing and trying to pretend the attack was something else entirely.
I think it is more than that. If Stevens, as has been reported, was involved in trafficking arms to AQ on behalf of the Obama administration, Obama had much more at stake than simply losing an election.