Norton knew Obama would be persuaded not to be a part of a film as he fought for the presidency - and he's glad he approached the politician before his advisors did.
He explains, "We thought, 'Maybe this guy will run for President in 2012...' and I went down and met him and we discussed the idea of a long-term political diary, chronicling his experiences... and they let us begin that.
"By the late summer of the first year that we were doing this... we began to grasp that this was going to happen now.
"I went back to him and said, 'I'm sure that everyone will tell you that this has gotta stop... I implore you, no matter what happens, this'll be an incredible window on the country and how people react to you candidacy.'
"Sure enough, when they set up the campaign team, they tried to scotch us immediately... and he stood up for it and said, 'I think this'll be an important record of the experience and they let us have an unprecedented amount of access."
The film, By the People: The Election of Barack Obama, will debut on U.S. TV network HBO next week (beg26Oct09).