20
ALEXANDER v. SOUTH CAROLINA STATE CONFERENCE
OF THE NAACP
Opinion of the Court
because the average District 1 in these simulations contained a higher BVAP than the District 1 in the Enacted
Plan.
The Challengers’ inference is flawed because Dr. Imai’s
models failed to consider partisanship. See J. S. A. Supp.
30a (acknowledging that “no race or partisan information
was used” (emphasis added)). That is a fatal omission in
this case. As noted, race and politics strongly correlate in
South Carolina, and Dr. Imai’s algorithm produced maps
without requiring that District 1 comply with the legislature’s asserted aim of ensuring that District 1 remain a relatively safe Republican seat. The effect of Dr. Imai’s omission can be seen by looking at the Democratic vote share
(measured by the results in the 2020 Presidential election)
in the versions of District 1 that his simulations produced.
President Biden’s vote share in the average District 1 in Dr.
Imai’s maps was significantly higher than his vote share in
the version of District 1 in the Enacted Plan. Rebuttal Report of Sean Trende in South Carolina State Conference of
the NAACP v. McMaster, No. 3:21–cv–3302 (D SC, Aug. 19,
2022), ECF Doc. 323–33, pp. 5–6. Indeed, Dr. Sean Trende,
the State’s expert, showed that District 1 would have voted
for the Democratic nominee in 2020 in 91% of Dr. Imai’s
simulations. Ibid. Because Dr. Imai’s model fails to track
the considerations that governed the legislature’s redistricting decision, it is irrelevant that the racial makeup of
District 1 in his maps differs from that in the version of the
district in the Enacted Plan.
It is also noteworthy that Dr. Imai could have easily controlled for partisan preferences just as he controlled for
other redistricting factors such as compactness and county
splits. He could have generated maps conditioned on District 1’s vote share matching or exceeding the Benchmark
Plan’s Republican tilt. But he did not take that obvious
step.