Fact check: Which California counties have the highest percentage of Republican voters?

1. Summary of the results

The analyses provided do not directly answer which California counties have the highest percentage of Republican voters. However, they reveal significant recent political shifts in the state. Ten California counties flipped from supporting Biden in 2020 to Trump in 2024: Orange, Riverside, San Bernardino, Inyo, Fresno, Merced, Butte, Nevada, San Joaquin, and Stanislaus counties ^[1]. Additionally, Trump increased his vote share in 45 of California's 58 counties in the 2024 election compared to 2020 ^[2].

The sources indicate that Republican voter registration has been experiencing both decline and recent growth. While Republican registration dropped from 28 percent in December 2024 to about 23 percent by June 2025 ^[3], there are also reports of Republican registration increasing while Democratic and independent registrations have declined ^[4]. In the Bay Area specifically, Trump's support was highest in Napa and Solano counties ^[5].

2. Missing context/alternative viewpoints

The original question seeks specific data on Republican voter percentages by county, but the analyses focus primarily on recent electoral shifts rather than baseline Republican registration data. This creates a significant gap in directly answering the question.

Missing critical context includes:

• Historical data on which counties have traditionally been Republican strongholds
• Actual percentage breakdowns of Republican voters by county
• Rural vs. urban voting patterns that typically influence Republican concentration
• The distinction between voter registration data and actual voting behavior

The sources suggest that California Democrats are actively working to maintain their political advantage through redistricting efforts to "strengthen their advantage in the state" ^[6], which indicates ongoing political maneuvering that could affect future Republican representation.

3. Potential misinformation/bias in the original statement

The original question itself does not contain misinformation, as it simply asks for factual data about Republican voter percentages by county. However, the lack of comprehensive data in the available sources means any definitive answer would be incomplete or potentially misleading.

The analyses reveal a potential bias toward focusing on recent electoral changes rather than providing the baseline demographic data requested ^{[2] [1] [7]}. This temporal focus on 2024 election results may not accurately reflect the counties with the highest overall Republican voter registration, as voting behavior can differ from party registration patterns.

Political organizations and media outlets benefit from emphasizing different narratives: Republicans might highlight the county flips and increased vote shares to suggest growing support, while Democrats might emphasize the overall decline in Republican registration to maintain their political messaging advantage.