California·CA·FIPS 06081

San Mateo County

Voted Democratic in 2024 · 330,510 votes cast

About San Mateo County

San Mateo County, officially the County of San Mateo, is a county located in the U.S. state of California. As of the 2020 United States census, the population was 764,442. Redwood City is the county seat, the third-most populated city in the county after Daly City and San Mateo.

2024 Presidential Results

All candidates · San Mateo County, California

Kamala D Harris(Democrat)

73.5%242,957

Won by 166,341 votes

Donald J Trump(Republican)

23.2%76,616

Other(Other)

2.8%9,250

Chase Oliver(Libertarian)

0.5%1,687

Margin History

Red = Republican, Blue = Democratic

2024D+50.3

2020D+57.7

2016D+57.2

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Swung Right in 2024

San Mateo County shifted 7.4 points toward Republicans compared to 2020. Voter turnout decreased by 11.7%.

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No one has claimed San Mateo County yet

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San Mateo County — Local Discussion

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Election data: MIT Election Data Science Lab, Harvard Dataverse (CC BY 4.0)