Through much of the 1990s, a newly hatched snake wreaked political havoc in the South. When North Carolina gained a seat in Congress following the 1990 census, it sought to rectify a long-standing failure to represent African American voters by creating, under federal pressure, two "majority-minority" voting districts. One of these snaked along Interstate 85 for nearly two hundred miles--not much wider than the road itself in some places--and...