How Are California’s Competitive Congressional Districts Changing

While California may not be a battleground in presidential elections, it's home to some of the nation's most hotly contested congressional races. With partisan control of the House of Representatives hanging in the balance, California's races will help determine the national political context moving forward. When we examined voter registration in these key districts, a surprising pattern emerged: a small but significant number of California voters are switching parties-and Republicans are benefitting.

The political ground in these districts may have shifted since the last congressional election two years ago. COVID-19 and its downstream effects have moved populations around the state. Meanwhile, California's automatic voter registration system has captured much of this movement with updated registration records, while boosting new registrations at the same time.

To understand what all this might mean for this year's election, we created an interactive feature that uses detailed registration data-including partisan, racial/ethnic, age, and language breakouts of voter registrants. It also highlights new and recently moved registrants, and voter turnout in the 2020 and 2022 elections. The following is our initial high-level analysis of this data.

California's competitive congressional districts (districts 3, 9, 13, 22, 27, 40, 41, 45, 47, and 49) are primarily clustered in three regions: the Central Valley, Orange County, and the Inland Empire east of Los Angeles. Currently, Republicans hold seven of the ten most competitive seats, with incumbents running in all but one-the open seat left by Democrat Katie Porter in District 47 in Orange County. In these ten competitive districts, 55% of likely voters currently favor the Democratic candidate and 41% favor the Republican candidate, according to PPIC's September survey.

In 2020, Joe Biden outperformed Donald Trump in all three of the seats currently held by Democrats, and even in five of the seven Republican-held ones. All the same, in the 2022 midterms-when these districts were first used after redistricting in 2020-the Democratic winners underperformed Biden and the Republican winners outperformed Trump. Half the districts (13, 22, 41, 45, and 47) were decided by margins under 5%.

In competitive districts, even small changes in voter registration can tip the scales. Changes to a district's underlying party registration can come from three sources: net new registrants (new California voters minus those who have left the state or otherwise dropped off the rolls), net registrant migration (voters moving between districts), and party switching (registrants changing their registration to a different party). At the time of this writing, we are able to examine these three sources of change for the period shortly after the last general election in 2022 to August 12 of this year.

Surprisingly, despite the upheaval of COVID-19, partisan migration since 2022 has been minimal. The 3rd district along the eastern border with Nevada and the 41st district in Riverside County have seen slight increases in both Democratic and Republican voters moving in, but even these changes amount to less than 1% of each district's registered population.

The changes from new registrants are somewhat larger and tend to favor independents (also known as no party preference). The largest changes are in two rematch races with Republican incumbents: District 13 in the northern San Joaquin Valley, where incumbent John Duarte is rematched against Adam Gray; and District 22 in the southern San Joaquin Valley, where incumbent David Valadao is rematched against Rudy Salas. In both districts there has been a large net surge of no party preference among new registrants. District 22 has also seen modest gains in other partisan categories, and the district has grown overall in its registered population.

At the other end of the spectrum, District 9 in San Joaquin County has experienced declines in all partisan categories. In fact, San Joaquin County's registered population declined even as its eligible population increased. The gap between these two numbers was among the largest of any county in the state, and by far the largest among the bigger counties with more than 500,000 eligible residents.

By far the largest source of partisan change has come from party switchers, and in particular voters switching from no party preference to Republican. These switchers have amounted to over 1% of the registered population in every competitive district-and the trend generally holds in districts not considered competitive this cycle as well. As switching to the Republican Party has grown, independent registration has declined across the board.

Much of this switching is likely the product of a somewhat more competitive Republican presidential primary, since participation required formal Republican registration (a constraint that did not apply on the Democratic side). However, in a few districts-9, 13, 22, and 27-the Republican gains have come more evenly from both Democrats and independents. These are mostly districts in the Central Valley, where Democratic registrants are known to lean conservative. Moreover, the switches since the primary have been dominated by Democrats switching to Republicans. Thus, some of the switching probably reflects a desire to better align party registration with broader political views in the context of a hotly contested election year.

As we approach the upcoming election, roughly half of likely voters say that they are more enthusiastic about voting than usual, with Democrats (62%) more likely than Republicans (46%) and independents (38%) to say this, according to PPIC's survey. Registration shifts in California's competitive districts could be an indicator of voter enthusiasm and may play a crucial role in determining control of the House. As California's congressional battlegrounds evolve, the political landscape of 2024 may continue to shift before election day. PPIC will monitor these races as we move deeper into the fall election season.

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