Gerrymandering 101
Published January 11, 2018 / Updated August 6, 2020

Gerrymandering 101

How to subvert American Democracy for fun and profit

by Chris Thomas

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Actual congressional districts in North Carolina

Thanks to the ruling of federal Judge James A Wynn Jr, North Carolina has joined a growing number of states in hot water over partisan gerrymandering. That may seem like dull stuff in the age of Trump, but gerrymandering is one of the oldest and most powerful tools in politics. It’s a coup in slow motion — a way to steal political power from the voters just by drawing a few lines on a map.

North Carolina’s map is particularly egregious but the state is fairly Republican to begin with, so the effects of gerrymandering are difficult to see there without some sophisticated statistical tools. To really get a sense of how gerrymandering works and why it’s so poisonous to democracy we have to travel north: to the Commonwealth of Virginia.

Warner, McAuliffe, & Kaine

In the above photograph, dated November 8th, 2013, Virginia Senators Mark Warner (D) and Tim Kaine (D) celebrate the election of Terry McAuliffe (D) to the governorship of their state. What is particularly interesting about this photograph is what the Virginia Congressional delegation looked like in the same year. Of the Commonwealth’s eleven Representatives to the House, just three were Democrats. Virginia elected two Democratic Senators, a Democratic governor, voted Democratic for President in 2008, 2012, and 2016 yet its House Delegation was and is 72% Republican.

Maps pulled from the New York Times

Partisan Gerrymandering.

To understand how that happened, consider these three maps of Virginia. On the top we have a break-down of votes for President, by county, in 2012. Virginia is interesting because it allows cities political autonomy from the surrounding counties so you can really see the urban/rural divide at work in those blue dots in the Western part of the state.

In the middle we have the breakdown of votes for Senator. There’s some variance, but not much. Virginia voters were willing to split tickets but overall that seemed to favor Democrats in 2012.

At the bottom we have the results of the House election for the same year. By drawing the lines between Virginia’s 11 congressional districts to favor Republicans, the map shifts. Democratic enclaves in near Washington DC are broken up — “cracked” — while Democratic counties near Richmond are lumped together — “packed.”

Cracking and Packing

These tools — packing and cracking — are the basic method by which gerrymandering works and we can see both evident in the congressional results from 2012.

Credit: New York Times

A few things should jump out at you. First, no Democrat won by less than 61% of the vote. That’s strange, because Virginia as a whole went for Obama in 2012 by just 51% to 49%, so high margins of victory are a bit counter-intuitive. Note, in particular, District 3: Democrats carried that district with a staggering 81% of the vote.

Second, note that no Republican won by more than 66% of the vote. In fact, the average Republican district was won with 58% of the vote as compared to the average Democratic district, won with 68% of the vote.

That ten-percentage-point difference is not a coincidence. Virginia redrew its Congressional map following the 2010 census and, when it did, both the state legislature and governorship were in Republican hands. The result was a map designed to waste Democratic votes.

Wasted Votes

The phrase “wasted vote” is not a jab at third-party voters but a way to think about how votes are reflected in the races they decide. Essentially, any vote beyond the minimum necessary to win a race or any vote cast for a losing candidate is “wasted.” In terms of the people who actually get into office, it is exactly as if those “wasted” votes were never cast.

How many votes? Well, in the 2012 election 1,806,025 Democratic votes were cast in Virginia and 1,304,842 of them were “wasted” by Virginia’s 2010 gerrymandering. That’s 72% of Virginia’s Democratic votes.

Of course, if losing votes are counted as wasted, there will always be wasted votes. Gerrymandering’s fingerprints are not in the presence of wasted votes but in the percentage of them.

Efficiency Gap

So can we quantify gerrymandering? If we compare vote wastage between parties we can get a sense of how gerrymandered a given map is and thus how much the political game is rigged in the favor of one party or another. One proposed method, called the “Efficiency Gap” takes the difference between the wasted votes for each party and divides that by the total votes cast. This gives us a single number representing the partisan skew of a given map. It allows us to quantify partisan gerrymandering.

For Virginia that works out to an efficiency gap of 21% in 2012.
Wisconsin’s efficiency gap in 2012 was 13%.
North Carolina’s estimated efficiency gap is 12%

While just simple arithmetic, that comparison is on the cutting edge of political science and has already seen action in the Supreme Court. The Court is currently mulling over Wisconsin’s map in Gill v. Whitford. Wisconsin appealed the case to the Supreme Court after a District court held that the state’s legislative districts “wasted” Democratic votes in violation of the 1st and 14th Amendments. While the Court has generally refused to strike down partisan gerrymandering in the past, Gill is the first challenge built around wasted votes and the efficiency gap specifically.

In theory an efficiency gap of 0% would indicate a perfectly balanced map but some gerrymandering is inevitable. In fact, states have a mandate under the Voting Rights Act to ensure that minority populations are not spilt up so as to deny them representation and the Court has been willing to enforce the VRA for some time. There is ample room, however, to accommodate protections against racial gerrymandering and partisan gerrymandering.

Experts generally hold that an efficiency gap larger than 7% “suggests a partisan skew that is likely to be large and durable.

Examining Virginia, Wisconsin, North Carolina and others in light of that 7% figure sheds new light on the stark difference between the US Senate, where Republicans hold a razor-thin margin, and the House, where the GOP majority is quite solid. Gerrymandering, not the will of the people, has determined the makeup of the lower chamber.

Tell Congress What You Think

While Resistbot doesn’t deliver briefs to the Supreme Court, your voice still matters on this issue. Thanks to Republican obstruction under President Obama there are a huge number of vacancies in the Federal Judiciary for President Trump to fill. Those judges will form the backbone of the Federal Court System for decades to come and their appointments are all subject to Senate confirmation hearings.

The judiciary is likely to be President Trump’s most lasting legacy but his appointments still require the Senate’s “advice and consent.” Text RESIST to 50409 to tell your Senators what you think about this or any other topic before Congress or use Facebook messenger to do the same thing by clicking here.

What about my state?

Curious what your state’s efficiency gap looks like? Consult the chart below, via Rollcall. Note that the gap is expressed here as a range; different turnouts result in different efficiency gap figures.

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