Mary at Pacific Views has a great post on why it's been such a hard long fight for the truth about Iraq to start chipping away at Bush's approval ratings. Basically, the issue is one of cognitive dissonance and the psychological theory of resistance. The more invested in an idea a person is, the more distress they will have at learning that they are wrong, and therefore the more likely they are to reject learning that they are wrong.
It's my theory, and I'm not sure how much the psychological establishment agrees with me, that one of the great weapons that wears down the resistance from cognitive dissonance is time. People are presented with new information and they reject it, but the information doesn't go away and they learn to live with it and their resistance goes down. You see this all the time with conservative thought--new things are immediately rejected but within a few years they are commonplace and conservatives are beginning to think they invented the new thing. Take civil rights as a good example. Conservatives resisted it and pandered to open racism. Now racism is considered wrong and many conservatives act like would be hitting the streets with MLK if it was happening today.
Anyway, the spinmeisters of BushCo know this happens and I think, unlike some of the commenters, that they knew that after it was revealed that they had lied to get us into Iraq, they could only buy a few months before the truth settled in and everyone started hating them. I doubt they thought they could hide it forever. They just had to hide it long enough to skate by in the next election.
And that's why the cover-ups were so haphazard. For one thing, cover-ups are always haphazard. But mostly I think that they didn't see their lies about Iraq (amongst other things) as long-term secrets. They just needed to stall the truth long enough to squeak past the election.
Timing the war was critical and they screwed up. It had to be close enough to 9/11 to use the events of that day to work people into a frenzy. But couldn't be too far from the election, because when the truth came out, cognitive dissonance was only buying them a year, max. My guess is that they thought they could draw out the are-there-or-aren't-there WMD's debate a little bit longer. But unfortunately for them, our military may be a little too good and they squelched the notion that there were tons of WMD's rather quickly.
So it's time for argument #2, which might have worked, since people were suffering from cognitive dissonance (are you sure I was wrong that the war was a good idea?) and they were grasping for relief. #2 provided that relief--we were there to save people. (See, it was a good idea.) And all the needed to do was stall those pictures of torture just long enough to coast through the election. But the couldn't do it.
And that's what they are doing with the censorship attempts at Fahrenheit 9/11. They don't really think that they can actually stop people from seeing this movie; they just want to stall it's release. At this point, an "every second counts" attitude has sunk in. The sooner people get the new information, the sooner their brains will start tearing down their resistance, which is low already due to their anger at the lies and the torture.
They're fooling themselves, though. The floodgates have opened and his poll numbers are beginning their dive. Stalling this movie for a month wouldn't help much. And I really do think by the time the Democratic Convention rolls around, people will be really open to what John Kerry might have to say.