In what has been described as the most important “one-person, one-vote” case since the Supreme Court adopted the principle over 50 years ago, the Court held that states may apportion state legislative districts based on total population. Local governments may do the same.  

The Court’s opinion in Evenwel v. Abbott is unanimous. All 50 states currently use total population to design state legislative districts; only seven adjust the census numbers “in any meaningful way.”   

In Reynold v. Sims (1964) the Court established the principle of “one-person, one-vote” requiring state legislative districts to be apportioned equally so that votes would have equal weight. The question in this case is what population is relevant—total population or voter-eligible population. Total population includes numerous people who cannot vote—notably non-citizens and children.

Following the 2010 census Texas redrew its State Senate districts using total-population. The maximum total-population deviation between districts was about 8 percent (up to 10 percent is presumed constitutional); the maximum eligible-voters deviation between districts exceeded 40 percent.

Justice Ginsburg’s majority opinion concluding Texas may redistrict using total population is “based on constitutional history, this Court’s decisions, and longstanding practice.”

Regarding constitutional history, Section 2 of the 14th Amendment explicitly requires that the U.S House of Representatives be apportioned based on total population. “It cannot be that the Fourteenth Amendment calls for the apportionment of congressional districts based on total population, but simultaneously prohibits States from apportioning their own legislative districts on the same basis.”

Regarding past decisions, in no previous cases alleging a state or local government failed to comply with “one-person, one-vote” had the Court determined if a deviation was permissible based on eligible- or registered-voter data.

And finally, states and local governments redistricting based on total population is a settled practice.  “Adopting voter-eligible apportionment as constitutional command would upset a well-functioning approach to districting that all 50 States and countless local jurisdictions have followed for decades, even centuries.”

Despite Texas’s urging the Court did not decide whether states may redistrict using voter-eligible population. It seems only a matter of time until the Court will decide whether state legislatures and local governments must redistrict based on total-population data.