What would be a fair district map in Arizona?

November 29, 2021 1:20 pm
Arizona redistricting flag

Illustration by VlatkoRadovic | iStock/Getty Images Plus

While fairness is not literally one of the six Arizona redistricting criteria, it should be everyone’s goal. 

In fact, the original proposition that Arizonans voted for to create the Arizona Independent Redistricting Commission has a preamble that gives its purpose as, “To oversee the mapping of fair and competitive congressional and legislative districts.”

The concept of fairness is intuitive to most people and is associated with our values, or the moral aspect of decision-making. If one party is supported with similar numbers of voters as another but only ends up with significantly fewer legislative representatives, it is unfair. You may like it if your preferred party has greater power, but isn’t a basic moral tenet to “do unto others as you would have them do unto you?” 


One attribute we’d like to see less of is something called “packing”. This is the term used to describe the choice of boundaries that put one party’s likely voters into as few districts as possible to diminish that party’s influence. It’s a practice that is rightfully viewed as unfair.

Most would agree that the packing of an opposition party’s supporters by those in power into a small number of districts is patently and morally wrong, no matter who does it. And people who believe in fairness in their private lives should not oppose it in their public choices.

Which brings us back to Arizona’s redistricting process, where legislative and congressional draft maps have been proposed by the AIRC. In the legislative map, the AIRC’s mapping consultants have projected vote shares for 16 districts that favor Republicans, and 14 that favor Democrats. This mismatch is not inherently unfair — from that information alone, one could reasonably conclude that the Republicans were favored in the state, which certainly would not be inconsistent with much of Arizona’s past.

But by how much is each party favored in the districts where they are likely to win? If Democrats are preferred by significantly larger margins, it would suggest that their populations are much more concentrated in these districts. And, in fact, the data bears this out. 

For instance, the average vote spread for Democratic districts is almost 10 percentage points higher than it is for Republican ones. This vote spread is the difference between the expected vote share for the two parties within each district, as estimated by the model adopted by the AIRC, based on average vote shares for nine previous elections.

The image below shows the projected vote spread, using the IRC’s numbers, for Republican-majority and Democratic-majority districts in Arizona, represented by red and blue lines, respectively. It’s clear that the Democratic districts have a much wider spread, with more districts having huge majorities. Only the rightmost red token, for District 30 in western Arizona, shows a comparable vote spread for districts favoring Republicans. 

On the other hand, statewide numbers suggest strongly that the parties have fairly even support in the state. The AIRC predicts a statewide vote spread of only 0.9%, and, which uses a different model, predicts a slight Democratic advantage of 51% compared to 49% for Republicans. Yet districts with an anticipated Democratic lean will tend to have much larger wins. 

This larger vote share should not be a point of celebration for Democrats. On the contrary, this means that votes that could have been useful for moving other districts in their direction have been “wasted” in a district they were already going to win. In short, some of these districts are “packed” with Democrats or others who tend to vote for Democratic candidates. And this might be a significant cause of the imbalance between the predicted number of favored districts for the two parties.

One caveat with calling this “packing” is that the term can imply a nefarious motivation on the part of those with the power to define district boundaries. While this sometimes occurs, I don’t think it’s constructive to assume it, particularly with a commission whose chair has publicly proclaimed her interest in doing her best for the entire state. 

Let’s appeal to the better angels of those who are volunteering their time to work on this very difficult problem. If the state is fairly evenly divided between those who prefer to vote for one or the other of the two major parties, let’s distribute the likely proponents with as little “waste” as is practicable. 

And to connect this discussion back to the constitutional criteria: it’s true that partisan balance — or specifically, a match between the statewide preference and the likely distribution in the legislature — is not an explicit requirement. And partisan balance could be satisfied with completely safe districts. In Arizona, you could have 15 safe Republican and 15 safe Democratic districts, and the competitiveness could be nil. 

But by packing Democrats into safe districts, and doing the same for Republicans, just not by as much, competitiveness is also damaged in the current map. If boundaries are adjusted from the current map to reduce the gap in extreme majorities, this will spread party-favoring population into other districts and increase competitiveness. And the appearance of fairness will be matched by actual fairness.

It’s win-win!


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Nelson Morgan
Nelson Morgan

Nelson Morgan, an Emeritus Professor at the University of California at Berkeley, is also a co-Director of Neighbors Forward AZ, a local non-profit dedicated to connecting good neighbors to achieve a peaceful, healthy society. He is the author of “We Can Fix It: How to disrupt the Impact of Big Money on politics”, with a foreword by George Lakoff.