The case, a challenge to voting districts for the Texas Senate, was brought by two voters, Sue Evenwel and Edward Pfenninger. They are represented by the Project on Fair Representation, the small conservative advocacy group that successfully mounted the earlier challenge to the Voting Rights Act. It is also behind a pending challenge to affirmative action in admissions at the University of Texas at Austin. In the new case, the challengers said their voting power had been diluted. "There are voters or potential voters in Texas whose Senate votes are worth approximately one and one-half times that of appellants," their brief said.
Urban areas are much more likely to be filled with people who cannot vote: noncitizens (especially Latinos), released felons whose voting rights have not been restored, and children. With districts redrawn using only voters rather than all people, there will be more Republican districts. Evenwel involves the issue of state legislature redistricting, but you can bet that if the challengers are successful in this case, they will argue for the same principle to be applied to the drawing of national congressional districts. It is not clear whether the ruling would apply to congressional districts, because the one-person, one-vote principle for congressional districts has a different source in the Constitution (Article I) than the 14th Amendment's Equal Protection Clause, which applies to state legislatures. But logically, the two cases are likely to be treated the same, and the result could be more congressional districts tending Republican, helping Republicans keep their advantage in the U.S. House of Representatives.