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Whenever I speak about our polarized politics, the first or second question I get is almost invariably about redistricting. Most Americans who know that our political system is not working the way it is supposed to don't know what specifically is wrong. But gerrymandering is something that clearly stands out for many. That is true even for Bill Clinton, who spoke about polarization and dysfunction at the 2013 Clinton Global Initiative and singled out gerrymandering as a prime cause.

The reality, as research has shown, is that the problem is more complicated than that. The "big sort," in journalist Bill Bishop's term, where Americans increasingly concentrate in areas where they are surrounded by like-minded people, is a major factor in the skewing, and the homogeneity, of districts. Other partisan residential patterns, including the fact that Democrats tend to live in more high-density urban areas, while Republicans tend to cluster in suburban and rural enclaves, matter. And the Senate, which represents states, not districts, is almost as polarized as the House. (Indeed, according to the National Journal voting records for the last Congress, it is more polarized—there was no overlap between the parties, meaning that the most conservative Democratic senator was to the left of the most liberal Republican senator.) Senate primaries, just like House ones, skew heavily toward each party's base, and senators respond. And the permanent campaign pushes lawmakers to stick with their team, even if some of the team's votes go against an individual member's more moderate or bipartisan grain.

But acknowledging all of that is not to say that gerrymandered districts don't have a significant impact on the sorry state of American politics. Gerrymandering has leached much of the broader heterogeneity out of congressional districts, contributing to the echo-chamber effect, where members' ideological predilections are reinforced, and not challenged, back home. A corollary is the racial segregation of districts—the fact that so many Republican districts now have barely more than trace elements of minorities, giving GOP lawmakers little incentive to reach out or be sensitive to issues that resonate with those groups. Partisan gerrymandering skews results away from the broader sentiments of voters in a state, as much research, including a new study by Duke University's Jonathan Mattingly and Christy Vaughn, demonstrates powerfully.

And, of course, gerrymandering has helped create a huge number of districts that are fundamentally safe for one party. This is sometimes done by a dominant party in a state "packing" the other party's districts to limit its chances in other districts. Other times it is done by an unholy alliance of both parties to keep all incumbents safe. Gerrymandering adds both to the homogeneity of districts and to making low-turnout primaries dominated by ideological activists the only meaningful elections.

More broadly, gerrymandering moves House and state-legislative elections away from any meaningful responsiveness to the will of the people. And the pattern of lawmakers choosing their voters instead of voters choosing their lawmakers creates more disaffection and cynicism among the public.

Almost every other democracy of significance avoids such problems by creating nonpartisan bodies to draw district boundaries.

How do we reform the redistricting process in this country? Through independent commissions that can use multiple criteria—not just equal population in districts, but factors such as competitiveness, compactness, and communities of interest—to create districts that more closely reflect broader public views. But creating independent commissions is no easy task; doing so through legislative action requires buy-in from the same lawmakers who draw the district lines—and who have the least incentive to give up their power via reform.