“sometimes, when it comes to gerrymandering, politicians press their advantages too far. Political scientists have a term for parties spreading their vote perilously thin through redistricting: dummymanders. The idea is that, by spreading a party’s voters more thinly across a greater number of districts in order to pick up more seats, a new map will turn strongholds into potential areas of danger. Instead of having five districts where the party can generally count on 60 percent support, say, they’ll create seven districts where their likely share is more like 53 percent — leaving more of them at risk during a wave election.”