This woman is an idiot. She and Nagin both have blood on their hands. TOTAL INCOMPETENCE by mayor and governor.
But I believe Blanco intentionally held off calling in the National Guard to restore order in New Orleans. She did this because she knows that if a white governor orders NG into a situation where they may be obliged to shoot black thugs, the "OJ/Rodney King/Malice Green" factor would come into play. She would be blamed for ordering the killing of some desperate and poor black men and she would never be reelected in Louisiana.
So she chose to wait, hoping that the firm hand would come from either Nagin or the President and they could shoulder the blame for the rough law enforcement.
It was a purely political decision on her part and she continues to play politics.