Another problem for would-be mapmaking wizards is demographic change; sometimes safely partisan “maps” unravel between redistricting cycles. A good example, in fact, is provided by Georgia’s Sixth and Seventh Congressional Districts, now occupied by Democrats Lucy McBath and Carolyn Bourdeaux, respectively, and now prime targets for Georgia Republican gerrymandering. In the last round of redistricting, these two North Atlanta suburban enclaves looked safely Republican. Both were carried by Republican congressional candidates from 2012 through 2018 by over 60 percent, and both were won by Mitt Romney with 60 percent in 2012.

But then a rise in Black and immigrant populations and lagging Republican strength among college-educated white voters changed everything quickly. The Sixth hosted a red-hot special election in 2017 in which veteran Republican Karen Handel edged future U.S. senator Jon Ossoff. The next year, McBath unseated Handel. Similarly, in the Seventh, incumbent Republican Rob Woodall took 60 percent in 2016 but then won over Bourdeaux by 419 votes in 2018. Woodall retired and Bourdeaux took the seat in 2020.

Effective gerrymanders must take into account both short-term and long-term partisan needs, which isn’t easy. And ruthless partisan redistricting must also sometimes yield right-of-way to the congressional ambitions of individual pols, many of them state legislators who are involved in the map-drawing process.