As Black voters stand to lose representation, one of the oldest civil rights organizations in the U.S. is leaning on a playbook that allowed it to radically increase Black political participation at the height of Jim Crow. Thirty-three congressional districts. Twenty-thousand volunteers. A $20 million investment. Those are some of the details behind what the NAACP says is its largest get-out-the-vote campaign for a midterm election in the organi…