LOS ANGELES — There’s no Helen Mirren this time around, no Forest Whitaker.

Unlike last year, when clear front-runners already had emerged in key categories, this awards season looks wide open.

About a dozen films could be considered viable nominees for best picture at the Academy Awards, and last week’s selection of “No Country for Old Men” as the year’s best by the National Board of Review of Motion Pictures doesn’t make the outlook much clearer. The Coen brothers’ beautifully brutal depiction of lawmen, guns and money along the Rio Grande has earned rave reviews and packed theaters in limited release, but it was expected to be a favorite even before it came out.

“I think that there are so many diverse genres, that there are so many strong performances, so many strong films,” said Annie Schulhof, president of the National Board of Review, which consists of film historians, students and educators. “This was very challenging to our group this year. Sometimes a film speaks to you and that’s what you stay with — that’s what ‘No Country for Old Men’ did.

“I think the race is wide open,” she added. “I would not call this a mediocre year at all.”

The competition for best actor is even more crowded. Hollywood typically offers stronger roles for men than women, but there were so many powerful, memorable ones this year that performances that might have seemed like obvious leads are spilling over into the supporting-actor category. That’s certainly true with “No Country,” in which Josh Brolin, Javier Bardem and Tommy Lee Jones share nearly equal screen time and are all essential to the story’s progression.

Miramax, which released the film, is pushing Brolin for best actor — his character is the one who finds the suitcase of cash left after a botched drug deal. Bardem, as the eccentric killer seeking the money, is the catalyst for much of the action, while Jones, as the Texas sheriff chasing both men, serves as the movie’s moral center and is the inspiration for the title.

“I agree it’s very difficult to separate them and decide who’s in best actor, who’s in best supporting actor, but we get guided by the academy on that and that’s the way they vote,” said Miramax President Daniel Battsek. “It’s doubly complicated by the fact that in both Josh and Tommy Lee’s case, they have other movies in which they will be, I think, quite possibly up for consideration in either supporting or base actor.”

Brolin could be a supporting-actor candidate for playing a corrupt cop in “American Gangster,” while Jones stars as a father investigating the death of his soldier son in “In the Valley of Elah.”

Other actors with nomination potential in a couple of categories are Philip Seymour Hoffman for “Before the Devil Knows You’re Dead” or “The Savages” (best actor) and “Charlie Wilson’s War” (supporting); Russell Crowe for “3:10 to Yuma” (best actor) and “American Gangster” (supporting); and Casey Affleck for “Gone Baby Gone” (best actor) and “The Assassination of Jesse James by the Coward Robert Ford” (supporting).

“Last year we had distinct front-runners in Helen Mirren (‘The Queen’), Forest Whitaker (‘The Last King of Scotland’) and ‘The Departed’ for best picture, simply because everyone in the industry was saying that Marty Scorsese was so overdue,” said Tom O’Neil, columnist for the awards Web site TheEnvelope.com. “The only cliffhanger was the fact that ‘The Departed’ wasn’t the typical Oscar-profile picture, being a kind of action thriller. This year, it’s totally up for grabs.”

O’Neil added that one film could emerge as an Academy Awards favorite over the next few weeks: “Sweeney Todd: The Demon Barber of Fleet Street,” Tim Burton’s screen version of the blood-soaked Stephen Sondheim musical starring Johnny Depp and Helena Bonham Carter.

“I think with the Johnny Depp cool factor and Tim Burton, it could have huge cult breakout status around Christmas. I could see a ‘Sweeney Todd’ bandwagon taking off and giving us a ‘Silence of the Lambs’-type sweep,” he said. ” ‘The Departed’ was evidence of the fact they’re not as squeamish as they used to be. I think they are tougher and grittier and trying to be cool, and that means taking ‘No Country for Old Men’ seriously as a best-picture nominee.

“‘Atonement’ is out front now,” he said of the sweeping, historical romance starring Keira Knightley and James McAvoy, the kind of movie Oscar voters traditionally have loved. “But I think it’s vulnerable.”

A breakdown of possible nominees, both locks and longshots, in the top categories:

BEST PICTURE: “American Gangster,” “Atonement,” “Charlie Wilson’s War,” “The Diving Bell and the Butterfly,” “Gone Baby Gone,” “Into the Wild,” “Juno,” “The Kite Runner,” “Michael Clayton,” “No Country for Old Men,” “Ratatouille,” “Sweeney Todd,” “There Will Be Blood.”

DIRECTOR: Ridley Scott (“American Gangster”), Joe Wright (“Atonement”), Sidney Lumet (“Before the Devil Knows You’re Dead”), Julian Schnabel (“The Diving Bell and the Butterfly”), Ben Affleck (“Gone Baby Gone”), Sean Penn (“Into the Wild”), Marc Forster (“The Kite Runner”), Tony Gilroy (“Michael Clayton”), Joel and Ethan Coen (“No Country for Old Men”), Tim Burton (“Sweeney Todd”), Paul Thomas Anderson (“There Will Be Blood”).

ACTOR: Russell Crowe (“3:10 to Yuma”), Denzel Washington (“American Gangster”), Brad Pitt (“The Assassination of Jesse James by the Coward Robert Ford”), James McAvoy (“Atonement”), Philip Seymour Hoffman (“Before the Devil Knows You’re Dead” or “The Savages”), Tom Hanks (“Charlie Wilson’s War”), Mathieu Amalric (“The Diving Bell and the Butterfly”), Viggo Mortensen (“Eastern Promises”), Casey Affleck (“Gone Baby Gone”), John Cusack (“Grace is Gone”), Richard Gere (“The Hoax”), Tommy Lee Jones (“In the Valley of Elah”), Emile Hirsch (“Into the Wild”), Ryan Gosling (“Lars and the Real Girl”), George Clooney (“Michael Clayton”), Josh Brolin (“No Country for Old Men”), Johnny Depp (“Sweeney Todd”), Daniel Day-Lewis (“There Will Be Blood”).

ACTRESS: Keira Knightley (“Atonement”), Julie Christie (“Away From Her”), Amy Adams (“Enchanted”), Ellen Page (“Juno”), Marion Cotillard (“La Vie en Rose”), Tang Wei (“Lust, Caution”), Angelina Jolie (“A Mighty Heart”), Laura Linney (“The Savages”), Helena Bonham Carter (“Sweeney Todd”), Halle Berry (“Things We Lost in the Fire”).

SUPPORTING ACTOR: Ben Foster (“3:10 to Yuma”), Josh Brolin (“American Gangster”), Russell Crowe (“American Gangster”), Casey Affleck (“The Assassination of Jesse James by the Coward Robert Ford”), Philip Seymour Hoffman (“Charlie Wilson’s War”), Max von Sydow (“The Diving Bell and the Butterfly”), John Travolta (“Hairspray”), J.K. Simmons (“Juno”), Tom Wilkinson (“Michael Clayton”), Javier Bardem (“No Country for Old Men”), Tommy Lee Jones (“No Country for Old Men”), Paul Dano (“There Will Be Blood”), Robert Downey Jr. (“Zodiac”).

SUPPORTING ACTRESS: Saoirse Ronan (“Atonement”), Olympia Dukakis (“Away From Her”), Julia Roberts (“Charlie Wilson’s War”), Amy Ryan (“Gone Baby Gone”), Cate Blanchett (“I’m Not There”), Catherine Keener (“Into the Wild”), Allison Janney (“Juno”), Tilda Swinton (“Michael Clayton”).