3 - When Politicians Draw the Maps

Summary

We investigate the role of politics in determining whether a map is drawn with partisan bias. We take a systematic look at the processes that states use to regulate the drawing of the lines through case studies and empirical analyses of redistricting outcomes, paying particular attention to one key variable: whether the maps were drawn by politicians. We find that the most biased maps occur in competitive states where politicians from a single party were able to draw the maps without having to work with the minority party. Our examination of the effects of bipartisan districting yields inconclusive results. In some cases, when the redistricting process requires two parties to work together to pass a plan, redistricting authorities draw the maps with low levels of seat–vote responsiveness, presumably as a result of the drawing of “safe seats” to benefit incumbents from both parties. However, in other cases, we do not see this outcome. We do find that, on average, bipartisan districting leads to a preservation of the status quo. In the states where two parties worked together to draw the maps, the level of bias in the post-2011 plans deviated little from the pre-2011 plans.