The general-election contest between California Sen. Barbara Boxer and Carly Fiorina has just begun, but even in a year when voters’ main concern is the economy, it’s already shaping up to be a potentially vicious battle over abortion rights. Though Boxer has long been the champion of abortion-rights groups, Fiorina has said she supports overturning Roe vs. Wade, the 1973 Supreme Court ruling that legalized abortion. And her endorsements by prominent anti-abortion groups, including the California ProLife Council and the Susan B. Anthony List, helped solidify her credentials as a conservative during the primary contest. Fiorina’s position puts her at...