Cite as: 602 U. S. ____ (2024)
25
Opinion of the Court
We have already rejected a plaintiff ’s expert report for
failing to account for this feature of mapmaking. In
Cromartie II, we faulted the plaintiff ’s expert for failing to
consider whether the excluded precincts “were located near
enough to [the district’s] boundaries or each other for the
legislature as a practical matter to have drawn [the district’s] boundaries to have included them, without sacrificing other important political goals.” 532 U. S., at 247. The
District Court clearly erred in crediting Dr. Ragusa’s models because his approach made that same mistake.
Dr. Ragusa’s report also carries less weight because of
how he measured a precinct’s partisan leanings. Using the
results of the 2020 Presidential election, Dr. Ragusa measured partisan tilt by looking at the total votes cast for President Biden, not the net votes for President Biden. This
method fails to account for the fact that voter turnout may
vary significantly from precinct to precinct, and therefore a
precinct in which a candidate gets a large number of votes
may also be a precinct in which the candidate fails to win a
majority. To illustrate this point, consider this simplified
example:
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District 1 shows that this is plainly untrue. (Links to some of the relevant precinct maps are provided below.) Many precincts would have had
to jump over quite a few others in order to join District 6. In addition,
the dissent ignores the other objectives that the new map sought to
achieve, namely, the unification of Beaufort and Berkeley Counties and
the division of Charleston between Districts 1 and 6 so that the city
would predictably have one Democratic House Member and one Republican House Member.
For the voting precincts in Beaufort County, see https://rfa.sc.gov/
sites/default/files/2024-01/Beaufort%20Precincts%202024.pdf. For Berkeley County, see https://rfa.sc.gov/sites/default/files/2022-04/Berkeley%
20Precincts.pdf.