On December 8, the Supreme Court will hear oral arguments in Evenwel v. Abbott, a challenge to Texas’s use of total population in drawing its state legislative districts. Registered voter Sue Evenwel argues that her vote is significantly diluted compared to those of voters in neighboring districts because, while the districts have roughly equal total populations, the other districts have large illegal alien populations. In other words, Evenwel’s district was allotted the same number of representatives as other districts that contained the same number of people but only half the number of eligible voters. She argues that this violates the “one person, one vote” guarantee of the Fourteenth Amendment’s Equal Protection Clause, established by the Supreme Court in Reynolds v. Sims (1964). This principle means districts must be drawn “on a basis that will insure, as far as is practicable, that equal numbers of voters can vote for proportionally equal numbers of officials.”

The Court has previously said states are free to choose which population to use in redistricting—unless it would otherwise violate the Constitution. For example, in Burns v. Richardson (1973), the Court upheld Hawaii’s decision to use registered voters as the basis for reapportionment because many people counted by the Census, such as members of the military temporary stationed there, were not registered to vote there. The Court previously declined to review a case presenting the same issue as Evenwel. Justice Clarence Thomas dissented from the Court’s refusal to hear that case, Chen v. City of Houston, saying that the Court “left a critical variable [of the one person, one vote principle] undefined,” which may be “of little consequence if we decide that each jurisdiction can choose its own measure of population.” 

The Court now may decide to define this part of the variable in Evenwel, and if it rules for the challenger, the decision could have a huge effect on state legislative districts across the country. Sean Trende of Real Clear Politics estimates “virtually every legislative and congressional district in the country would have to be redrawn,” and this could result in a shift towards more Republican-dominated districts.

To read more about this case, check out the latest issue of Engage.