Late salvo against the favourite opens up race

It was, as usual, Oprah Winfrey's show that best captured the mood of an expectant nation this week, when the venerable film critic Roger Ebert used her sofa to declare this year's Oscars one of the most "predictable" of modern times.

The race for every major acting prize is dominated by a long odds-on favourite: Jeff Bridges for Best Actor and Sandra Bullock for Best Actress, together with Christoph Waltz and Mo'Nique in the supporting categories.

Yet while the destination of Best Picture and Best Director, the night's biggest prizes, might have seemed equally obvious when Mr Ebert made his picks, recent events have conspired to seriously muddy the water.

After weeks of heavy favouritism, The Hurt Locker has faced a string of unfortunate – and some might say suspiciously-timed – setbacks as the race reaches its climax. First, there was the ugly business of the Iraq war film's producer, Nicholas Chartier, being banned from the event for sending out an email seeking to persuade voters not to vote for "some $500m film" like Avatar. Then, both the LA Times and Washington Post ran extensive hit pieces in which US troops rubbished the film's portrayal of their trade. Finally a soldier once interviewed by Hurt Locker's Oscar-nominated writer Mark Boal sued the producers, claiming that the film was a not-so-subtle portrayal of his career.

The controversies have combined to change the Best Picture race as it enters its final furlong. You can now get better than even money about The Hurt Locker, once 5/4 on, on Betfair. Avatar once touched 6/4 at one stage but is now creeping towards favouritism. Supporters of Bigelow's small-budget, independent film may wonder if it has fallen victim to a smear campaign co-ordinated by ruthless campaigners for more expensive rival titles.