Once a decade, after each census, states embark on a mission to redraw the lines of their Congressional districts. States can draw district lines in any fashion they like as long as the district map follows three basic rules: 1) the districts must be congruous, 2) they must contain roughly the same numbers of voters, and 3) they must not obviously discriminate against minorities. More often than not, redistricting is a political process — in 37 out of 50 states today, state legislatures have the power to draw those lines, which means that the majority party has an opportunity to create districts that give them an electoral advantage. This process has a name – gerrymandering – coined in 1812 to describe a district designed by then-Governor Elbridge Gerry of Massachusetts that looked like a salamander. Today, gerrymandering is the reason some districts look like this or this.

Do both parties do it?

Yes, maps in various states give advantages to both parties. Republicans have the advantage in states like Texas, Pennsylvania, and North and South Carolina. 

Democrats have a leg up in states like Minnesota, Maryland, and New York.

Does gerrymandering affect the balance in Congress?

Gerrymandering as it exists today appears to advantage Republicans. An analysis by the Associated Press looked at a measure called the efficiency gap, which is the difference between how many seats you would expect each party to win based on its population and how many seats each party wins in reality. The researchers found that “among the two dozen most populated states that determine the vast majority of Congress, there were nearly three times as many with Republican-tilted U.S. House districts.” The advantage was even more pronounced in state legislatures, where there were four times as many Republican-tilted districts.

Does gerrymandering suppress minority voters?

It can. In 1985, the Supreme Court expanded the Voting Rights Act of 1965 to combat an earlier form of racial gerrymandering: the practice of spreading minority voters out thinly to dilute their electoral influence. The Court did this by requiring states to create majority-minority districts — districts in which racial minorities comprise the majority of voters. This did lead to more minority elected officials, but over time, has begun to have an unintended side effect. Now, some states appear to be packing minority voters so densely into minority districts that their influence is once again diminished. Legal challenges against racial gerrymandering have been brought in several states, including North Carolina, Virginia, and Texas.

Does gerrymandering explain why Congress is so polarized?

While gerrymandering is often blamed for polarization in Congress, political scientists largely say that research casts some doubt on that claim. Party affiliation has an even greater effect on how members of Congress vote than the will of their constituents, says John Sides of George Washington University. That means that members of Congress are not only out-of-step with the average American, says Sides, but with their own bases as well.

To be sure, there are fewer competitive House districts than there used to be. A study by Cook Political Report found a 56percent decline in the number of competitive seats in the House since 1997. However, they attribute 83 percent of that decline to factors other than redistricting. Even in competitive districts, elected officials are polarized. When an incumbent loses to a candidate from the other party, the winner is likely to be from the more extreme wing of that party, something Joseph Bafumi and Michael Herron call “leapfrog representation.”

Larry Kramer, a former dean of Stanford Law School, points to the Senate as evidence that gerrymandering isn’t the primary force behind polarization. Voters elect their senators on a statewide basis, without the influence of districts, yet the Senate remains highly polarized.

Can I trust my state’s electoral map?

Perhaps the clearest impact of gerrymandering is on voters’ trust in the system. Politicized redistricting appears unsavory, and voters sense that it’s unfair. After all, it’s a fundamental principle of democracy that voters choose their representatives, not the other way around. As one political scientist says, “Even if its effects on polarization are as small as I believe them to be, the practice of elected politicians drawing districts for themselves and their political allies is an invitation to overt corruption. A key to any successful democracy is a widespread belief in the fairness and impartiality of elections. Having incumbents participate in designing districts promoting their job security does little to enhance the legitimacy of American democracy.” Many organizations, including the Bipartisan Policy Center, advocate for independent redistricting commissions, which are less likely to be politicized.

Is there another side to this debate?

Kevin Williamson, writing for The National Review, argues that there can be no such thing as an independent commission, and that any redistricting process will be inherently partisan. If voters think gerrymandering is unfair, he says, they should boot out the elected representatives who do it.  (Of course, if opposition votes are negated by  gerrymandered district lines, that’s easier said than done.)

Are there examples of alternative plans for drawing district lines?

Yes. One group of experts in particular re-drew lines for each congressional district in the nation to illustrate how district lines might influence voting outcomes.

What I can I do to advocate for fairer redistricting?

Read on!