Guerrilla filmmaker catches out McCain

The independent internet video that's triggered a right old row in the United States over John McCain's property ownership - he said on camera that he wasn't sure how many houses he owned - was made by Robert Greenwald, (pictured) a 62-year-old New Yorker who is fast getting a reputation as an awkward documentary maker to rival Michael Moore's.

Greenwald has made a number of viral videos during this election campaign, attacking first Rudy Giuliani then John McCain. They are 'independent' in the sense that the Obama camp has not commissioned paid for them. But they're anything but independent in that they are designed to boost Obama and cause his rivals the maximum discomfort.

Until recently, Greenwald's success as a TV and film director was mixed. He received Emmy nominations for 21 Hours at Munich - about the massacre at the 1972 Olympics - and for The Burning Bed, which starred Farah Fawcett in a story about domestic abuse. But he also made Xanadu, a critical flop starring Olivia Newton-John. The New York Times once described his work as "commercially respectable B-list movies".

But in recent years, he has started making hot-topic documentaries and has never looked back. His acclaimed work includes Outfoxed: Rupert Murdoch's War on Journalism and Iraq For Sale: The War Profiteers.

And then he discovered the political potential of the viral video. He told the BBC recently: "We said: 'Let's see if we can use the new technology, not where it had been primarily used - which was naked women falling down in showers and other high cultural events like that - but we could use it for political storytelling'. And we've just passed 23 million views on our videos."