My student Matthew Cooke and I have written this piece for Slate. It begins:

California Republicans, now joined by the Trump administration’s Department of Justice, have sued California in federal court to stop implementation of Proposition 50, a voter-passed ballot measure that creates a Democratic gerrymander of the state’s congressional districts, adding up to five more Democratic seats. The lawsuit argues that the Legislature had an unconstitutional race-focused intent on the state’s Latino voters when it passed the maps. In fact, whatever the Legislature intended should be irrelevant to the Republicans’ claim, and they likely will lose because California voters were acting with a predominantly political, not racial, intent.

If Republicans lose the Prop 50 lawsuit and the United States Supreme Court does not interfere with a new federal district court ruling putting Texas’ new gerrymander on hold for 2026, Democrats could have an advantage going into 2026, even as the Supreme Court contemplates even more changes in redistricting rules in its pending case out of Louisiana….

The Republicans’ complaint in California will likely focus on evidence regarding the supposed intent of members of the state Legislature and particularly the intent of Paul Mitchell, a redistricting consultant who drew the new lines for the Legislature. Republicans argue that the evidence shows that racial considerations predominated in drawing those lines. It’s a tough argument to make, because the Legislature seemed motivated to do a Democratic partisan gerrymander to counter Texas’ partisan gerrymander of congressional maps favoring Republicans. Any racial considerations were simply to make sure that the new proposed maps did not violate the Voting Rights Act, as it currently stands.

But there is a far more serious threat to Republicans’ argument about racial predominance—they may be focusing on the wrong actors’ intent. To understand this argument, we need to look at the kind of law Proposition 50 was. Back in 2008 and 2010, California voters adopted plans through voter initiatives to have redistricting done by independent commissions, not the Legislature. Under the California Constitution, the Legislature could not simply pass its own law reversing the voter-approved use of commissions for the state’s congressional districts. Instead, the Legislature had to authorize a ballot measure to be approved or rejected by voters suspending use of the commission-drawn lines for Congress. Proposition 50 asked voters to approve the new maps that Mitchell drew and the Legislature proposed, maps that would only come into effect if California voters approved. This is key: Because California voters’ were the ultimate decision-makers, we should be asking in any racial gerrymandering case if California voters, not the state Legislature, had a predominantly racial focus.

So how to prove the intent of the voters? After all, voters don’t meet like a legislature in a great hall and debate the finer points of legislation. Under California law, courts look first to the text of a ballot measure. When that text does not unambiguously disclose the electorate’s intent, courts next look to official ballot materials to clarify the electorate’s understanding of the measure’s impact. These materials can include the official summaries of the impact, which the California attorney general is required to prepare, or text included in the “voter information guide,” also known as the “ballot pamphlet” mailed to every registered voter in California. Indeed, the California Supreme Court has held in the analogous context of interpreting the meaning of a voter initiative that the “opinion of drafters or legislators who sponsor an initiative is not relevant since such opinion does not represent the intent of the electorate and we cannot say with assurance that the voters were aware of the drafters’ intent.” As another California appeals court wrote in 2005, the only materials for courts to look at when it comes to voter intent are those ballot materials.

With respect to Proposition 50, the California ballot materials show exclusively partisan intentions. Beginning with the quick-reference guide at the very start of the 2025 ballot pamphlet, voters were met with a set of explicitly partisan arguments. The quick-reference guide provided an argument in support of Proposition 50 on the grounds that it would “counter Donald Trump’s scheme to rig next year’s congressional election.” Meanwhile, the quick-reference guide describes Proposition 50 as follows: “AUTHORIZES TEMPORARY CHANGES TO CONGRESSIONAL DISTRICT MAPS IN RESPONSE TO TEXAS’ PARTISAN REDISTRICTING.” It also includes an argument against adoption on the grounds that Proposition 50 would remove “protections that ban maps designed to favor political parties.” Neither argument identifies nor even alludes to racial considerations. Instead, concerns over partisan advantage predominate. Likewise, the attorney general’s summary (included in the ballot pamphlet) describes Proposition 50 as a response to “Texas’ mid-decade partisan redistricting.” (Importantly, nothing in the Proposition requires Texas’ gerrymander to be upheld for Proposition 50 to remain in effect.)….

Whether or not California voters were justified in “fighting fire with fire” by engaging in a Democratic partisan gerrymander to counter Republicans’ partisan gerrymander in Texas—and if the Texas plan is blocked and the California plan upheld, Donald Trump will have made things far worse for Republicans—the point here is that it was California voters who made the ultimate call. And the evidence leaves no doubt they were acting as naked partisans, not motivated at all by the racial considerations necessary to make out a claim for racial gerrymandering as the Supreme Court has explained it….