Cite as: 602 U. S. ____ (2024)
23
Opinion of the Court
Using this approach, he first identified the five counties
that have at least one precinct that fell within District 1 in
the Benchmark Plan. These counties in their entirety constituted the “county envelope.”
Dr. Ragusa employed a method that we will discuss below
to control for the partisan preferences of voters in these precincts, and he also controlled for precinct size. He then
asked whether a precinct of a given size with a given partisan breakdown was more or less likely to be included in District 1 depending on its racial demographics, and he reported that districts with a high percentage of black voters
were more likely to be excluded.
His remaining model looked only at the precincts that
were in District 1 in the Benchmark Plan, and controlling
in the same way for size and partisan leaning, he reported
that a precinct was more likely to be moved out if it had a
high percentage of black voters.
All three of these models exhibit the same flaw. Because
they did not control for contiguity or compactness, they all
assume that a precinct could be moved into or out of District
1 regardless of its distance from the line between that district and District 6. That is highly unrealistic. A simple
example illustrates this point in relation to the county envelope approach, as can be seen with a quick look at Figure
1, which we again reproduce below.