One of the best years in American film history was supposed to come to a triumphant conclusion Sunday night with a serious Oscar throwdown between Steven Spielberg's historical epic "Lincoln" and "Zero Dark Thirty," Kathryn Bigelow's tense and gritty take on the killing of Osama bin Laden.

Some other very good films -- "Argo" and "Silver Linings Playbook" -- were also in the hunt. But in early January, nearly all the Oscar pundits, from insider blogs and critic surveys to the statistical analysis of economist David Rothschild who writes for the Huffington Post, had the two films based on actual events in a slugfest for best picture.

This film image released by Warner Bros. Pictures shows Bryan Cranston, left, as Jack O Donnell and Ben Affleck as Tony Mendez in "Argo,"  a
This film image released by Warner Bros. Pictures shows Bryan Cranston, left, as Jack O Donnell and Ben Affleck as Tony Mendez in "Argo," a rescue thriller about the 1979 Iranian hostage crisis. (AP Photo/Warner Bros., Claire Folger) ( Claire Folger )

But, as has often been the case in the race for the Oscar, things changed -- and very quickly. The result of all the twists and turns of this particularly unusual awards season have the Hollywood gods smiling down upon "Argo" -- yet another movie based on real events -- as the prohibitive favorite to take home the gold statute.

The Ben Affleck thriller about the rescue of American hostages from Tehran, Iran, in the 1970s has made a huge comeback to favorite status. But the turning point for the film came with a snub that seemingly knocked it out of the running for the top prize.

When the Oscar nominees were announced Jan. 10, there were two stunning absences -- both in the best director category. One was Bigelow; the other was Affleck. Their failure to make the list unleashed an uproar in film industry circles. No one had a quarrel with any of the five directors nominated, but Bigelow and Affleck had been considered sure things.

As things go in Hollywood, "it might as well be raining tadpoles," New York Times film industry writer Michael Cieply wrote at the time.

All kinds of reasons were offered for the snubs. The most plausible is that the voters in the directors' branch of the Academy of Motion Picture Arts and Sciences (who decide the nominees) may have assumed that Affleck and Bigelow were such locks they decided to throw a vote the way of Michael Haneke ("Amour") and first-timer Benh Zeitlin ("Beasts of the Southern Wild").

But no film has won the top prize without its director at least being nominated for best director since 1989, when "Driving Miss Daisy" won even though its director, Bruce Beresford, was snubbed. So, it appeared "Lincoln" (Spielberg is a director nominee) had grabbed a commanding lead, and the chances of "Argo" and "Zero Dark Thirty" had been dealt a serious -- if not fatal -- blow.

In the case of "Zero," that proved to be the case. Battered by controversies over its accuracy and the visceral reaction of filmgoers (including some Academy voters) to the movie's torture scenes, it quickly faded from contention. That Bigelow, screenwriter Mark Boal and Sony Pictures, the movie's studio, were slow in responding to the criticisms and rather strained when they finally did certainly didn't help.

In addition, because of those torture scenes, "Zero" really doesn't make you feel that great about America. "Argo" and "Lincoln," on the other hand, make you feel pretty darn swell about your country. (That some of the heroes in "Argo" are characters based on real-life filmmakers who helped in the escape certainly didn't hurt the film with Academy voters.)

But while "Zero" was fading, Affleck, who is well-liked and regarded within the business, and "Argo" took off on incredible run through the major pre-Oscar awards. Affleck won best director and "Argo" was named best drama at the Golden Globes -- with the crowd at ceremony, including many likely Oscar voters, giving both director and movie roaring ovations.

"Argo" went on to win best ensemble at the Screen Actors Guild Awards (SAG's equivalent of best picture), Affleck won best director from the Directors Guild and, on Feb. 10, "Argo" snagged best film and best director from the British Academy of Film and Television Arts.

In pool, they call that running the table.

One unintended side effect of the "Argo" surge is that some of the drama has been drained of what had been a particularly competitive Academy Awards. In fact, many of the leaders in the top Oscar categories now appear to be mortal locks, starting with "Argo."

Daniel Day-Lewis has been the runaway leader for best actor since "Lincoln" premiered in the fall. Anne Hathaway, Fantine in "Les Miserables," became the front-runner for best supporting actress almost since the first film clip of her singing "I Dreamed A Dream" was released. Nothing has changed since.

Despite the occasional gaffe in her acceptance speeches, Jennifer Lawrence ("Silver Linings Playbook") has emerged as a heavy favorite to top Jessica Chastain ("Zero") for best actress. (One hedge: If rumblings in Hollywood are to be believed, 85-year-old Emmanuelle Riva of "Amour" is coming on late as a possible spoiler.)

The only top category that remains a true horse race is best supporting actor, where any one of four out of the five nominees could win. Good luck in the office pool picking a winner from among Tommy Lee Jones ("Lincoln"), Robert De Niro ("Playbook"), Christoph Waltz ("Django Unchained") and Alan Arkin ("Argo").

At the end of the evening, though, you can count on some true emotion when Affleck is among those who will receive the best picture Oscar. It will be a rare case when a snub from your peers worked out just fine in the end.

And the next day: well, there are going to be more than a few folks feeling badly for Spielberg, who has not won a best picture Oscar since "Schindler's List" 20 years ago. He may have seen this all coming when, after losing to Affleck at the DGA Awards, he sighed, "There have been moments when I wish it was a slightly less incredible year for movies."

For the latest on the Oscars, film news and more, follow Charlie McCollum at Twitter.com/charlie_mccollu.