San Ysidro, CA Political Map | Democrat & Republican Areas in San Ysidro

By the BestNeighborhood data science team. Last updated May 2026.

San Ysidro leans Democratic by roughly 24 points: about 62% of voters vote Democratic and 38% Republican.

 

About 41% of adults in San Ysidro typically vote, below the U.S. average of about 62%. Among adults in San Ysidro, ~25% vote Democratic, ~16% Republican, and ~59% don't vote. The map below shows estimated turnout by block group.

How San Ysidro compares

Among cities within 25 miles, San Ysidro leans more Democratic than 19 of 21 neighbors.

Politically, San Ysidro sits close to the rest of California.

Politics vary noticeably by neighborhood within San Ysidro. The west side is the most Democratic-leaning (D+28) and the east side is the least Democratic-leaning (D+11), a spread of about 16 points.

Why San Ysidro leans the way it does

This analysis examined 14,881 data points per city to find what predicts political lean and turnout. The items below are a few correlations that stood out for San Ysidro, not a ranked or complete list of what matters most.

Dense areas vote Democratic. About 95% of residents in San Ysidro live in densely developed areas, about 58 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 38% of adults in San Ysidro have never been married, above 92% of cities.

Walkability and Democratic lean

Places with a highly walkable street grid tend to lean Democratic; San Ysidro, CA sits in the top tenth nationally on this measure. A walkable street grid does not change how people vote; it mostly reflects how urban a place is.

Why turnout in San Ysidro looks the way it does

Areas with limited routine healthcare access turn out at lower rates. San Ysidro is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 48%, about 14 points below the California average of 62%. Renters vote less often than owners, and about 60% of households in San Ysidro rent, compared to around 43% in nearby cities. High food insecurity lines up with lower turnout, and about 32% of adults in San Ysidro report food insecurity, above 97% of cities. Learn more about the findings and methodology on the political spectrum map.

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Sources and methodology

Precinct-level voting records used to fit the model come from California Secretary of State, Elections, distributed by the Voting and Election Science Team. Demographic inputs come from the U.S. Census Bureau (ACS 5-year estimates and the 2020 Decennial Census). Health and environmental inputs come from the CDC (PLACES and the Environmental Justice Index). Land cover comes from the USGS and EPA. Election-day and lead-up weather come from PRISM 4km daily grids and the NOAA Global Historical Climatology Network. Mail-voting and election-administration patterns come from the MIT Election Lab's Survey of the Performance of American Elections. Block-group crime detail comes from CrimeGrade. Internet data and modeling support provided by ISPreports.org.

Modeling and analysis by the BestNeighborhood data science team. Full methodology and findings: political spectrum map.

Methodology reviewed by the BestNeighborhood data team. Last updated May 2026.