Ontario, CA Political Map | Democrat & Republican Areas in Ontario

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

Ontario leans slightly Democratic by roughly 12 points: about 56% of voters vote Democratic and 44% Republican.

 

About 44% of adults in Ontario typically vote, below the U.S. average of about 62%. Among adults in Ontario, ~25% vote Democratic, ~19% Republican, and ~56% don't vote. The map below shows estimated turnout by block group.

How Ontario compares

Among cities within 25 miles, Ontario leans more Democratic than 52 of 83 neighbors.

Ontario runs about 8 points more Republican than California as a whole.

Politics vary noticeably by neighborhood within Ontario. The northeast side is the most Democratic-leaning (D+23) and the southeast side is the least Democratic-leaning (D+4), a spread of about 19 points.

Why Ontario 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 Ontario, not a ranked or complete list of what matters most.

Dense areas vote Democratic. About 98% of residents in Ontario live in densely developed areas, about 61 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 43% of adults in Ontario have never been married, above 95% of cities.

Walkability and Democratic lean

Places with a highly walkable street grid tend to lean Democratic; Ontario, 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 Ontario looks the way it does

Areas with limited routine healthcare access turn out at lower rates. Ontario is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. Renters vote less often than owners, and about 42% of households in Ontario rent, about 17 points above the U.S. average of 25%. High food insecurity lines up with lower turnout, and about 26% of adults in Ontario report food insecurity, above 92% 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.