They just need to keep hammering that one point and Hillary will be toast:
"Ambassador Stevens asked for more security. Why didn't you give it to him?"
Hillary answers, "Our security consultants advised it was not warranted."
Ask again, "In the matter of personnel security, why didn't you err on the side of caution when the ambassador kept repeating his request for more security?"
Rinse and repeat three dozen times, if need be. Just don't let up on that one point.