The NCSL Blog


By Lisa Soronen

By the end of June, when the Supreme Court decides Arizona State Legislature v. Arizona Independent Redistricting Commission.we will know if state legislatures can be completely cut out of the redistricting process.

By the end of June 2016 we will know who gets to decide which population measure complies with one-person-one-vote: the state legislature or the Supreme Court.

The U.S. Constitution Equal Protection Clause’s “one-person one-vote” principle requires that voting districts have roughly the same population so that votes in each district count equally.  In Evenwel v. Abbott the Supreme Court will decide if state legislatures will retain their authority to choose the population metric they prefer--total population or total voting population.

While state legislatures may prefer to decide for themselves—rather than have the Supreme Court tell them—what population metric is appropriate, they may disagree about the better metric.

Texas reapportioned its state Senate districts following the 2010 census based on total population alone. All parties agree the redistricting plan’s deviation from the ideal (8 percent) using total population is acceptable. But plaintiffs claim that depending on which voter-based metric is used (citizens of voting age, registered voters, etc.) Texas’s plan “deviates from the ‘ideal’ district by roughly 46 to 55 percent.” Plaintiffs claim that their votes are worth less than other voters because they live in districts that substantially deviate from the “ideal” in terms of number of voters or potential voters, which violates the “one-person one-vote” principle.

The district court ruled in favor of Texas reasoning that the Supreme Court has never held any particular metric to be unconstitutional. Rather, the Court has stated that a population measure is viable as long as it is not the result of a discriminatory choice by the state legislature (which was not alleged in this case).

The Court agreeing to hear this case ranks as a surprise. Over the last 25 years the Supreme Court has denied certiorari in at least three other petitions (all involving local governments) arguing that voter population must be equalized in districts. Election law professor Richard Hasen wrote on his blog, "Like Texas, I had considered the issue fairly settled by the Supreme Court that states have the power to decide whether to use total population or another measure for drawing district lines."

Lisa Soronen is the executive director of the State and Local Legal Center and writes frequently for the NCSL blog about the U.S. Supreme Court.

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This blog offers updates on the National Conference of State Legislatures' research and training, the latest on federalism and the state legislative institution, and posts about state legislators and legislative staff. The blog is edited by NCSL staff and written primarily by NCSL's experts on public policy and the state legislative institution.