The new book “Trailblazer: An Intimate Biography of Sarah Palin,” finally reveals what exactly it was that propelled Mrs. Palin from small-town mayor to state governor to Republican vicepresidential nominee. Her bun. Singular. “The updo had been a standard style for Sarah since her days as Wasilla mayor,” writes author Lorenzo Benet, an editor at People magazine. “By keeping her hair in a bun and away from her face, Sarah always believed she could keep someone’s attention during a meeting or a conversation.