On Monday night they waited to snatch the first autographed copies of the memoirs of the former Democratic president Bill Clinton.

On Wednesday they went to watch Michael Moore's Fahrenheit 9/11, a film aimed, at least in part, at ending the incumbency of the current Republican president, George Bush.

The film officially opens today in 900 cinemas - three times as many as for Mr Moore's previous film, the Academy Award-winning Bowling for Columbine. But New Yorkers got an early sight, along with premiere-goers in Washington DC.

What was billed as the launch of a film, however, looked more like the beginning of a political campaign.

Both left and right encouraged their supporters to write, email and fund-raise to either talk up or rubbish the movie, while the Democrats and the White House are wondering respectively how to capitalise on the film or minimise its impact.

The Washington showing was attended by several prominent Congress figures, while in New York activists of the Democratic National Committee collected money outside the cinema, from which people emerged after seeing the film saying they were moved to tears. The Bush administration had heated discussions on how to respond, with those who advocated a blitz of refutations losing to others who believed it best to ignore the film rather than give it credibility.

Like Mel Gibson's film The Passion of the Christ, which energised the right, the disputes reveal a huge overlap between politics and culture in this election year.

"I can't think of any precedent for [the furore over Moore's film] in a presidential campaign," Frances Lee, a political science professor at Case Western Reserve University, told the Washington Post. "As a marketing phenomenon it seems to echo The Passion [of the Christ]: intense enthusiasm, organised groups buying tickets with proselytising zeal, the sense that one is getting something that corporate America wanted to stifle."

One liberal advocacy group, MoveOn.org, is holding meetings on Monday around the country so members can discuss the film. It has also alerted its 2.2 million members, asking them to pledge to see the film in its opening weekend, and is providing spokesmen and women for comment on the movie at venues in swing states. MoveOn says it is acting at least in part to counter conservative efforts to stop the film being screened. For, in a symbol of the extent to which America has become polarised, if Moore is loved by the left, he is no less loathed by the right.

A documentary, Michael Moore Hates America, which lambasts his methodology, is to be released; and a book, Michael Moore is a Big Fat Stupid White Man, will be published next week - a riff on the title of his bestseller Stupid White Men.

A conservative group, Move America Forward, has called on members to lobby their local cinema chains to stop them screening it.

"Since we are the customers of the American movie theatres, it is important for us to speak up loudly and tell the industry executives that we don't want this misleading and grotesque movie being shown in our local cinema," said the group's director, Siobhan Guiney.

A letter-writing campaign by the group persuaded CBS to drop a TV documentary on Ronald Reagan held to be too disrespectful of the late president, but this time the group may fail.

"There has been some communication, but not an overwhelming amount. And we do intend to play the film," said Dick Westerling, the spokesman for one cinema chain, Regal Entertainment Group, which has 6,020 screens in the country.

David Bossie, head of another conservative group, Citizens United, has accused Moore of violating federal election laws: "Moore has publicly indicated that his goal is to impact this election."

There is some truth to this. "It's my personal aim that Bush is removed from the White House," says Moore, who has hired former Clinton operatives as a rapid response unit to any attacks that impugn the film's integrity. "But if the movie can inspire a few of the 50% of the Americans who do not vote to get involved and be engaged, then that is important."

While the film is far more subtle than Moore's previous work, there are few who have seen it who believe it will convert anybody who has not already made up their mind. But what it could do is galvanise those who may vote to get organised, and encourage those not inspired by the Democratic candidate, John Kerry, to go to the polls to remove Mr Bush.

To the charge that he was speaking to the choir, Mr Moore said: "I'm very happy to speak to them, because that choir has been asleep. If I can give them a song to sing as they leave the theatre and become active once again, that's a good thing."