"A renowned legal scholar tells the definitive story of Hollingsworth v. Perry, the trial that will stand as the most potent argument for marriage equality. In 2008, California voters passed Proposition 8, rescinding the right of same-sex couples to marry in the state. Advocates for marriage equality were outraged. Still, major gay-rights groups opposed a federal challenge to the law, warning that it would be dangerously premature. A loss could set...