Will Hayes (RYAN REYNOLDS) is an ad executive who's just received the final divorce papers from his wife. Yet, the one good thing that came from their marriage is young daughter Maya (ABIGAIL BRESLIN) whose recent sex-ed class has left her with many questions. While Will uncomfortably skirts around the biological ones, he does agree to tell Maya a bedtime story of sorts about her mother, although his changing of names will leave the girl guessing which one turns out to be the mom she's known all her life.
We then flashback to 1992 when Will is about to leave his college sweetheart, Emily (ELIZABETH BANKS), back in Wisconsin for two weeks while he travels to New York City to work on Bill Clinton's presidential campaign. Despite Will's ideals and speechwriting abilities, his boss, Gareth (ADAM FERRARA), relegates him to fetching coffee and stocking the bathrooms with toilet paper.
Apolitical copy girl April (ISLA FISHER) finds that amusing, but fellow campaign worker Russell McCormack (DEREK LUKE) likes Will's perseverance, with the two becoming travel roommates when Will extends his two-week commitment. Later, he meets aspiring journalist Summer Hartley (RACHEL WEISZ) who's dating Hampton Roth (KEVIN KLINE), her much older thesis advisor and published author.
As the years pass and political work comes and goes, Will ends up falling for, involved with, the object of desire for, and/or breaking up with Emily, April and/or Summer, with Maya closely following the details of his recounted story, trying to figure out which one ends up being her mother.