Michael Moore's film Fahrenheit 9/11 has taken at least $8.2m (£4.5m) at cinemas across North America on its first day, distributors say.
Moore already holds the box office record for a documentary
Moore's assault on President George Bush and the Iraq war is on course to top the weekend box office chart.
The film stirred up controversy when it made its debut at the Cannes Film Festival earlier this year, where it won the coveted Palme d'Or award.
British audiences will get to see the film after its UK release on 9 July.
It has benefited from the controversy it has caused in the US, with right-wing groups urging boycotts of the film and liberal lobbyists promoting the movie.
Disney refused to allow its Miramax subsidiary to release the film because of its political content, prompting Miramax founders Harvey and Bob Weinstein to buy the rights back, and strike their own deal with Lions Gate Films and IFC.
"It always helps when there's a group out there that says, 'Don't go see this movie, it's bad for you,'" IFC president Jonathan Sehring said.
'Blows away' records
Paul Dergarabedian, president of Exhibitor Relations, which compiles box office statistics, compared the furore over Fahrenheit 9/11 to Mel Gibson's The Passion of the Christ, which was at the centre of a storm after claims it was anti-Semitic.
The film features interviews with parents of soldiers killed in Iraq
"It's like how The Passion of the Christ redefined what a certain genre of movie could do at the box office, Fahrenheit 9/11 is doing the same thing," he said.
"This blows away any conceivable box office record for a documentary."
The current US box office record for a documentary is held by another Moore film - Bowling for Columbine, which took $21.6m (£11.9m) during its run in 2002. It took a further $35m (£19.2m) outside the US.
Its nearest competitor, comedy White Chicks, is said to be $1.5m (£823,000) behind Fahrenheit 9/11 - but is showing at three times as many cinemas.
Michael Moore's film begins by recounting Mr Bush's disputed election victory and goes on to allege connections between Mr Bush and influential Saudi families, including the Bin Ladens.
However, it is Mr Bush's response to the 11 September attacks and the subsequent war in Iraq that forms the main focus of the film.
Moore builds a case that Mr Bush stoked public fears to win widespread support for a needless invasion of Iraq.
Both positive and negative reviews have described the film as "propaganda".