I just saw
Fahrenheit 9/11
(which was screening at (ironically enough) the George in St Kilda as a fundraiser for the Greens). I was impressed. In this film, Michael Moore basically goes from the 2000 US Presidential election (which he mentions briefly) to the present day, piecing together facts from many sources into a coherent whole, with a good deal of opinion and some humorous editing. Thankfully he keeps his trademark attention-grabbing clowning to a minimum, and focuses on presenting the story of these past four years as he sees it (and it's not a pretty picture: the current US administration, and much of the US economy, is in the pockets of untouchable Saudi interests, whom it is protecting from 9/11 investigations, instead using the aftermath of the incident to grab power and maximise its cronies' profits, whilst manipulating the American public into a constant Orwellian state of fear and screwing over the poor working stiffs sent to fight in its dubious war). It's not a happy story to watch (and some of the images of war casualties are graphic), though I'd say it is an important film to see.
It's telling that, when Fahrenheit 9/11 was released, Disney's hastily assembled riposte to it was a piece of neo-Norman Rockwell kitsch about "American values". The implicit message being "don't think, feel; asking questions causes trouble; go back to sleep, you'll feel better".
But yes, I think that Fahrenheit 9/11 has the potential to cost Bush the next election (notwithstanding wildcards such as trick voting machines, suspensions of elections, or Osama bin Laden's pre-election capture, of course). It won't sway the true believers in either camp, who are already decided, but it could electrify many of those who are currently uncertain, or who would otherwise not have voted.