MONTGOMERY, ALABAMA — More than 30 years apart, two women separately set forth on long drives south to Alabama. Their backgrounds were different, their mission the same: to join an existential fight for the soul of American democracy. Viola Gregg Liuzzo, a White 39-year-old married mother of five from Detroit, went first. In 1965, she was appalled by images from Bloody Sunday, when state troopers tear-gassed and brutalized voting rights activists who were attempting to cross the Edmund Pettus Bridge on a march from Selma to Montgomery. When Dr. Martin Luther King Jr. and John Lewis asked Americans to come...