How Do You Draw a Fair Map? Don't Make Partisan Balance Your Goal.

The national redistricting wars have reached new heights. Kicked off by Texas’ mid-decade redistricting at the insistence of President Trump, California, Virginia, Missouri, and Ohio have all joined the fray, with Maryland, Florida, Indiana, and other states potentially jumping in soon.

This has brought up old debates about what exactly makes a fair map. Activists for fair maps have almost always prized proportionality as the first priority. Essentially, that maps should try to reflect the statewide popular vote as closely as possible.

The debates seem almost quaint now, given how nuclear the gerrymandering wars have gotten ahead of the 2026 midterms. But it’s worth keeping in mind what principles should undergird fair maps. Oftentimes, power is split in a state, and parties must compromise, or the state uses an independent commission. In these situations, it’s important that the maps are guided by intelligent principles that build public confidence in the process and resulting maps.

Contrary to conventional wisdom, a fair map should not set out to have the partisan breakdown of the districts reflect the most recent statewide election. So, for example, a fair map in Wisconsin should not set out to be 4R - 4D given that the state is fairly evenly divided overall.

This seems counterintuitive, given that, generally, people spot a gerrymandered map by the fact that it doesn’t reflect the statewide popular vote, and is instead slanted towards one party. To be clear, this is not to say that partisan balance is bad, or that maps are better if they are imbalanced. Balance can be, and often is, a positive for a potential map. This is to say, however, that explicit partisan balancing should not be the first, or even a major, goal at the outset for map drawers. But why?

For one, partisan balance is forever a moving target. A map that is balanced one cycle may become horribly unbalanced the next due to changing coalitions and normal election-to-election shifts. Even slight statewide shifts may not be evenly distributed across districts, throwing even the most carefully calibrated map out of balance. This problem is compounded by the fact that in some states, the only way to achieve “balance” is to give one party a large number of seats that lean only slightly towards it. This may cause that “balance” to backfire.

In fact, this is sometimes seen in gerrymanders. After the 2016 election brought huge numbers of suburban voters into the Democratic coalition, many seats drawn to be Republican-leaning suddenly became competitive or even Democratic-leaning. Given maps are expected to last ten years, this becomes a major issue if a “fair map” has a large number of seats drawn to be “just right.” Of course, gerrymanders still have more imbalance over the long run, as partisanship does stay broadly stable in the short term. But the uncertainties inherent in elections mean that explicit balancing is not the cure-all advocates claim.

On top of that, balance may actually reduce voter confidence in the maps. One common talking point from voters against the gerrymanders of the 2010s was that different parts of their town, or even different parts of their street, were in different districts. Explicit partisan balancing often requires splitting up towns or cities to ensure that one party’s votes are efficiently distributed across districts, as opposed to being “packed” too tightly. Of course, any map will have to draw its lines somewhere, and someone will always be across the road from a different district. But map makers can increase voter confidence when these dividing lines coincide with other, familiar dividing lines such as county or municipal boundaries.

Even factoring in partisan balance can lead to incoherent districts. For example, some independent commissions prioritize keeping certain areas together, but then also prioritize partisan balance. This leads to odd choices, where seemingly obvious areas are split up, all because the commission prioritized a different set of areas earlier in the process. Forgoing an explicit focus on partisan balance can eliminate needing to make these kinds of choices.

Balance is also difficult to apply across states. In Massachusetts, for example, it’s impossible to draw more than one Trump-won district, despite him winning 36% of the vote. But in much of the Midwest, it’s trivially easy to draw maps that reflect the statewide popular vote. This raises the question of how far map makers should go when trying to make proportional maps. How contorted can districts be in an effort to make a map that reflects the statewide vote? Having to draw a line, so to speak, at some level of compactness opens the door to bias from map makers who may subconsciously try harder to balance some states compared to others.

Instead, map makers should prioritize geographic continuity, keeping together counties, municipalities, and metro areas. This is a more objective set of criteria that can be consistently applied across states. It also raises public confidence in the redistricting process and the resulting maps. Voters see their districts as making intuitive sense and aligning with their own understanding of the “boundaries” in the area.

What’s more, geographic continuity, if applied across all states, tends to yield essentially balanced maps, a better result than balanced maps which look odd and contorted to voters. This is because geographic continuity advantages Republicans in some states and Democrats in others. While it’s true that compact maps tend to have a Republican slant in states like Wisconsin, Tennessee, Kentucky, and Indiana, virtually all Republican geographic advantage is wiped out by California and New England alone. For example, in California, a compact map often yields under ten Trump-won seats (out of 52 total), despite him winning nearly 40% of the vote.

The idea that compact maps advantage Republicans is somewhat of an outdated idea. This was true in the early 2010s, when Republicans had a much more “efficient” distribution of voters. The Democratic coalition often relied on massive margins in a small number of areas, while Republicans won many areas 55-45, for example. This meant a compact map in a state may yield one heavily Democratic district and four districts that leaned Republican. But in recent years, Democrats have seen the “efficiency” of their coalition massively increase. Losses in cities and rural areas, combined with big gains in suburbs, have made compact maps much more Democratic leaning than they would have been 12 years ago. This is another reason why chasing partisan balance is often an elusive goal.

Ultimately, the focus on explicit partisan balancing over geographic continuity may be a relic of a different time. In the 2010s, Democrats were largely the party pushing anti-gerrymandering activism. At the time, compact maps in key swing states like Wisconsin and Pennsylvania really did lean Republican. But times have changed, and continuing to prioritize explicit partisan balance in maps over geographic continuity does more harm than good in the long run.