The book Game Change: Obama and the Clintons, McCain and Palin, and the Race of a Lifetime raced to the top of best-seller lists in 2010 because it provided behind-the-scenes details of the compelling 2008 presidential election.

 

The film Game Change, which debuts on HBO Saturday at 9 p.m. ET, covers only half the story.

Not Barack Obama's election as the nation's first African-American president; instead, Game Change zeroes in on how little-known Sarah Palin, governor of Alaska for less than two years, became John McCain's running mate and zoomed into the stratosphere of political celebrity.

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"I just thought it was by far the most compelling story in that book," director Jay Roach says.

McCain's last-minute decision to tap Palin offered a tight story within a short time frame, less than 60 days from the announcement to Election Day. Screenwriter Danny Strong calls it "one of the most amazing political stories of our time."