Exposing the illicit arms smuggling operation to Syrian fighters with links to terrorists was too close for comfort to the Fast and Furious scandal. So Benghazi had to be covered up at all costs.
An administration caught twice being involved in unsavory gun running operations would have been politically weakened, right before an election. Even now, concerns that the public would view these operations as being similar strikes fear in the administration. This is one area where hypocricy might come back to haunt the president.
Romney should have campaigned harder. He had all kinds of ammo he refused to use.