Those of them that don't.........weren't voting Romney anyway.
Romney is not able, cannot do anything about Benghazi NOW. When he is President, then he can get involved.
Romney is simply avoiding being trapped into this by the MSN's, who then would say "He doesn't know what he is talking about, or Why is he putting his 2cents worth in, or SEE there Romney is Politicizing it".
Romney thinks he is winning, and there will be no resolution on this before the election. So throwing out accusations and challenges is counterproductive at this point.
Besides, this is the job of CONGRESS and the MEDIA. Whether they will do there job is up for debate.
Romney being so cautious shows you they like their internal polling.