The tight Oscar race for Best Actress between the presumed co-frontrunners, Silver Linings Playbook’s Jennifer Lawrence and Zero Dark Thirty’s Jessica Chastain, took a few twists and turns this weekend. But will any of it affect the outcome one way or another? Momentum is a fickle thing — you can win it or lose it  in an instant.

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Both young stars are coming off a stellar week where they won Golden Globe and Critics Choice Movie Awards for their performances. And now, just 2 1/2 weeks before Oscar voting begins and smack in the middle of SAG balloting, Chastain pulled off the neat trick of starring in the No. 1 and No. 2 films at the box office (#1 Mama and #2 Zero Dark Thirty). Before Mama opened, some pundits observed that starring in a standard horror film in the midst of Oscar crunch time could hurt Chastain the same way Norbit’s Oscar-time release was perceived to hurt Eddie Murphy when he lost for Dreamgirls. But in fact Mama received generally good reviews (62% fresh at Rotten Tomatoes) and way overperformed at the box office, helping to make the emerging Chastain an even bigger star. And the fact that she simultaneously continues in her Broadway run in The Heiress (a film based on the play won Olivia DeHavilland an Oscar) also helps as voters love actors who move between theatre and movies with ease.

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