LOS ANGELES (Reuters) - Just three months ago, "Zero Dark Thirty" looked like a strong contender for the movie industry's biggest prize.

But when the Oscar for Best Picture is handed out on Sunday, the thriller about the decade-long U.S. hunt for, and 2011 killing of, Osama bin Laden is unlikely to get its name engraved on the coveted gold statuette.

After a fierce campaign over the movie's depiction of torture that started in Washington and extended to human rights groups, "Zero Dark Thirty" went from front-runner to also-ran at the Academy Awards.

Despite winning early honors from influential critics in New York, Washington, Boston and Chicago, pundits say the failure of "Zero Dark Thirty" to win traction in Hollywood may have as much to do with its style as the heated debate it has provoked.

"It's a little cool," said Dave Karger, chief correspondent for Fandango.com.

"Usually you need some kind of crowd-pleasing element to have a shot at winning Best Picture at the Academy Awards, and that is what (Iran hostage drama) 'Argo' has. It has a great rousing emotional aspect to it which 'Zero Dark Thirty,' by design, does not have," Karger told Reuters.

'GROSSLY INACCURATE'?

Early signs of trouble for "Zero Dark Thirty" came in mid-December when U.S. Senators Dianne Feinstein, John McCain and Carl Levin sent a letter to movie studio Sony Pictures.

They called the film "grossly inaccurate and misleading" for suggesting torture helped the United States track the al Qaeda leader to a Pakistan compound.

The senators cited intelligence records released in April 2012 that showed this was not the case and said the movie "has the potential to shape American public opinion in a disturbing and misleading manner."

Director Kathryn Bigelow and screenwriter Mark Boal said repeatedly that the film shows a variety of intelligence methods, not all of which produced results.

Three weeks later, Bigelow was omitted from the Oscar's Best Director shortlist, chosen by about 5,800 movie industry professionals who make up the Academy of Motion Picture Arts and Sciences.

Bigelow was only one of four big directors to be snubbed, and "Zero Dark Thirty" received five Oscar nominations, including one for Best Picture. But Los Angeles Times film critic Kenneth Turan was among those who pointed the finger at Washington.

"Chalk up this year's (Oscar) nominations as a victory for the bullying power of the United States Senate and an undeserved loss for Kathryn Bigelow," Turan wrote in January.

In a column in The Wall Street Journal on Thursday, deputy editor Daniel Henninger agreed.

"Had Senators Feinstein, Levin and McCain not saddled up their high horses in a December 19 letter to Sony Pictures denouncing the movie, 'Zero Dark Thirty' would not now be out of the running for Best Picture at the Oscars," Henninger wrote.

Pete Hammond, awards columnist at entertainment industry website Deadline.com, said the political attacks on the film certainly had an impact before "Zero Dark Thirty" was released in U.S. movie theaters nationwide in late January.

"But when it opened wide, it actually helped by bringing so much publicity, and now there has been a backlash against the backlash," Hammond told Reuters.

FIGHTING BACK

By late January, Bigelow and Boal were making speeches, getting magazine profiles, and writing opinion pieces in which they directed critics to the U.S. officials who sanctioned, or turned a blind eye, to harsh interrogation techniques.

Victims of the September 11, 2001, attacks ordered by bin Laden voiced their support, as did departing U.S. Defense Secretary Leon Panetta, who called it a "great movie."

Steve Elzer, spokesman for Columbia Pictures, the Sony Pictures unit behind the film, said the studio was very proud of the movie, saying it had generated "an amazing national conversation."

"'Zero Dark Thirty' has been a huge critical and commercial success that has also been praised by a large number of experts, historians and academics outside of the political arena.

"No matter how we do at the Oscars on Sunday, we know this will be a motion picture that will be remembered many years from now. We couldn't be more proud to have been associated with this film," Elzer told Reuters.

Despite the furor and small protests by human rights activists at some awards ceremonies, "Zero Dark Thirty" has won stellar reviews and reaped more than $100 million at the worldwide box office, most of it in North America.

Review aggregator website Rotten Tomatoes gives the film a 94 percent positive rating. Oscar Best Picture favorites "Lincoln" and "Argo" score 89 percent and 96 percent respectively.

Yet "Zero Dark Thirty" has picked up just one major prize in the Hollywood guild awards for directors, actors, producers and writers that are considered a predictor of Oscar success.

Boal won the Writers Guild of America trophy for Best Original Screenplay last weekend, and is a strong contender for the Oscar in that category on Sunday.

Jessica Chastain is thought to have a good chance at taking home the Best Actress prize for her performance as the feisty young CIA agent credited with tracking down bin Laden in the face of skepticism from her bosses.

"Jessica Chastain is a good place to put your 'Zero Dark Thirty' vote if you are wounded by the backlash against the film and want to express your support some place," said Tom O'Neil, of awards website Goldderby.com.

However, the film, which is being promoted as the "most-talked about movie of the year," is seen as a long shot.

"Controversial movies suffer with Academy voters. I think 'Zero Dark Thirty' will have a tough time winning Best Picture because I think the Academy is going to go with less controversial choices," Rotten Tomatoes editor in chief Matt Atchity said.