It saddens me to say that while I'd like to blame the Bush administration, and the SCLM, for perpetuating the idea that Saddam may have had anything to with 9/11, I honestly can't. While they share some responsbility - the fact that 70% of the American public believes this cannot solely be blamed on this.
While the Bushies did their part, the truth is this ability to be completely ignorant about the Most Important Day In Recent History has less to do with the success of the Bushies' attempts to perpetuate this idea, and more to do with peoples' willingness to embrace the idea of collective guilt. I'm fairly sure that any poll question which replaced Saddam's name with any other prominent Arab or Persian leader (assuming there was one with name recognition) would receive a similar affirmative response.
One towel-head is as good as another.