Every ten years following the census, state legislatures use the new population count to redraw the district boundaries used by the state legislature and Congress in order to adjust for population change. How the lines are drawn depends on which party controls the legislature and whether their plan can survive a veto by the governor or legal challenge.
The decennial rite of having sitting lawmakers choose their voters before voters get to choose them has always been an exercise of democracy in reverse.
In recent decades, the development of high tech redistricting software and unprecedented access to voting and election data has brought pinpoint precision to the redistricting process. It allows state legislators, left on their own, to gerrymander district lines for political or personal gain.
Redistricting is so finely honed that you can predict which party will win any given seat with 80-90% accuracy. With so few competitive races, it is little wonder that the public sees the system as rigged.
Several states have adopted bipartisan redistricting commissions so as to inject nonpartisanship. But do they? Bipartisan commissions are typically made up of equal numbers of Republican and Democratic officeholders and a neutral member whom the two parties agree on to be the tie-breaking vote. They are prone to self-dealing among the two parties.
Nonpartisan commissions, similar to those used in Colorado, California, and Michigan are a better option for creating more impartial maps. Among their characteristics are:
Eleven states had redistricting commissions with primary responsibility for drawing the maps for the state legislature and Congress. Of those, four states (Michigan, Colorado, California, and Iowa) use a fully non-partisan process with minimal to no legislative interference, while the other eight states have bipartisan commissions.
The fully nonpartisan states did the best to create fair maps. Michigan’s commission reduced by two the number of seats previously gerrymandered by the dominant republican party and added one more highly competitive seat. Colorado also added one more competitive seat and kept the balance between the two parties. Bipartisan commissions had predictably mixed results, often leading to court intervention, only improved when the courts were called on to intervene.