Next week, the Supreme Court will hear oral arguments in Evenwel v Abbott, in which a group of Texans is asking the Court to reconsider how congressional districts are apportioned.

The plaintiffs in the case contend that since congressional districts are drawn based on how many people (as opposed to eligible or registered voters) live in a given geographic area, non-citizens inflate the voting power of citizens in congressional districts with large numbers of non-citizens. And since the non-citizen population is unevenly distributed, this means that one vote carries more relative weight in some districts as opposed to others.

There are a number of problems with changing this arrangement such that districts are drawn based on the number of eligible voters, as opposed to total population. For starters, the Census doesn’t collect the necessary data. But even if they did, changing the system to exclude non-voters would effectively deny representation to those non-voters. And non-voters — be they children, the mentally disabled, felons or non-citizens — still have a vested interest in the actions the government takes, even if they can’t vote on them.

To get a sense of which districts would be most and least affected by adopting the eligible voter standard, sociologist Andrew Beveridge has put together an interactive map plotting the percentage of people in each congressional district that are not eligible to vote. As you can see, the districts most-heavily affected are predominantly (though far from exclusively) in the Southwest, particularly with large Latino populations.

<iframe src=”http://www.socialexplorer.com/evenwel/”</iframe>

As Beveridge wrote regarding his methodology:

To create a real world comparison, this analysis used the same data that would have been available for redistricting in 2011 (the 2010 Census and 2006-10 American Community Survey, from which the Census Bureau tabulates CVAP for various ethnic and racial communities down to the block group level). If the court should rule for the plaintiffs, the Census Bureau would be forced to adjust their methods to accommodate the ruling, which could include adding a question about citizenship to the decennial censuses. (This report does not take into account any other problems with such a change, but several of the briefs filed in Evenwel do discuss such issues, including whether adding such a question would jeopardize the response rate and accuracy of the census.) This analysis reveals that the effects of ruling for the plaintiffs in Evenwel would be extensive. Not only would most statewide districting plans in the United States need to be redrawn, but more than half of all districts would be substantially changed based upon the change from the population to the potential voter criterion. The newly drawn districts would shift power to those districts with lower proportions of non-citizens and children under 18. The demographic shift in voting power would also substantially favor increasing the number of Republican-dominated districts.

His analysis confirms one of the greatest fears voting rights advocates have concerning the Evenwel case: that it will make it difficult to draw majority-minority districts in conjunction with the Voting Rights Act, and would shift the Congressional map even more in favor of Republicans than it already is.

While there is precedent for using the eligible voter standard when applying the “one person, one vote” principle, the uneven effects it would have if applied nationally suggest that it won’t (or at least shouldn’t) apply in this case. As Garret Epps wrote in the Atlantic in May:

In a 1966 case called Burns v. Richardson, the Court approved a temporary Hawaii districting plan based on the number of eligible voters; the state argued it needed to use that basis, rather than population, because of the large number of military personnel moving in and out of the state. Justice William Brennan’s majority opinion approved Hawaii’s temporary plan “only because” it “produced a distribution of legislators not substantially different from that which would have resulted from the use of a permissible population basis.”

Beveridge’s analysis shows that if the Supreme Court rules in favor of the plaintiffs in Evenwel, it will become virtually impossible for Democrats to win the House, regardless of how wide their margin of victory is in the national popular vote. This suggests that, as with previous conservative arguments concerning ballot access, the case has less to do with being right and more do to with winning.