How Dark Money Helped Republicans Hold the House and Hurt Voters

From the linked article:

Redistricting is supposed to protect the fundamental principle of one-person-one-vote. As demographics change, lines are shifted to make sure everyone is equally represented and to give communities a voice. In order for Republicans to win in North Carolina, they undermined the votes of Democrats, especially African-Americans. (Party leaders in North Carolina say they were simply complying with federal voting laws.)

The strategy began in the run-up to the 2010 elections. Republicans poured money into local races in North Carolina and elsewhere. It was an efficient approach. While congressional races routinely cost millions, a few thousand dollars can swing a campaign for a seat in the state legislature.