- Lead
- 67,563
- Total
- 237,232
- vs nation
- D+30.0
California 18th Congressional District
President margin by year
Place winner margin
President results by year
Modeled candidate-vote estimate on current district boundaries
- Lead
- 114,274
- Total
- 267,314
- vs nation
- D+38.3
- Lead
- 99,029
- Total
- 212,528
- vs nation
- D+44.5
- Lead
- 79,552
- Total
- 194,925
- vs nation
- D+37.0
- Lead
- 82,514
- Total
- 202,961
- vs nation
- D+33.4
- Lead
- 51,927
- Total
- 188,372
- vs nation
- D+30.0
- Lead
- 43,022
- Total
- 171,740
- vs nation
- D+24.5
- Lead
- 36,719
- Total
- 160,039
- vs nation
- D+14.4
Key facts
- 2024 presidential margin
- D+28.5MIT Election Lab
- Population
- 770,1912024 5-year
- Population density
- 130 / sq mi2024 5-year · TIGER/Line
- Land area
- 5,921 sq miTIGER/Line
- Median household income
- $103,5172024 5-year
- White (non-Hispanic)
- 19.0%2024 5-year
- Black
- 1.9%2024 5-year
- Hispanic / Latino
- 65.6%2024 5-year
- Peak Democratic margin
- D+46.6 in 2016MIT Election Lab
- Peak Republican margin
- R+47.5 in 1924MIT Election Lab
- Most similar
- Congressional District 29, CA · twin score 93.7
presidential history
Party record book
California 18th Congressional District · the strongest Democratic and Republican presidential performances recorded here, measured three ways.
1892–2024 (partial returns from 1876) · 38 presidential cycles · 38 with a vote-share denominator · 34 with a national benchmark
Highest vote share
Largest share of the presidential candidate vote cast here.
Democratic
Joe Biden2020
70.3%
187,901 votes · D+42.7 · modeled estimate
Runner-up · Hillary Clinton, 2016 · 69.9%
Republican
Warren G. Harding1920
65.9%
7,883 votes · R+39.4 · modeled estimate
Runner-up · Herbert Hoover, 1928 · 61.4%
Most votes
Largest number of votes cast for the party’s presidential nominee here.
Democratic
Joe Biden2020
187,901votes
70.3% of the vote · D+42.7 · modeled estimate
Runner-up · Kamala Harris, 2024 · 148,675 votes
Republican
Donald Trump2024
81,112votes
34.2% of the vote · D+28.5 · modeled estimate
Runner-up · Ronald Reagan, 1984 · 80,389 votes
Best relative to the U.S.
This Place’s margin against the national margin in the same election — positive when it leaned toward the party more than the country did.
Democratic
Hillary Clinton2016
+44.5pts D vs U.S.
Place D+46.6 · U.S. D+2.1 · modeled estimate
Runner-up · Joe Biden, 2020 · +38.3 pts
Republican
Calvin Coolidge1924
+22.3pts R vs U.S.
Place R+47.5 · U.S. R+25.2 · modeled estimate
Runner-up · Warren G. Harding, 1920 · +13.2 pts
Current officeholders
Federal officeholders only. State and local officeholders are planned for the next data pass.
Senate and governor results are in the Office selector at the top of this page.
U.S. House
Each result reflects the U.S. House district as it was drawn for that election; redistricting has redrawn these lines over time, so they can differ from the current 120th-Congress district shown on the map above.
CA-18 spans the heart of Santa Clara County, where a highly educated, tech-sector workforce has pushed Democratic presidential margins above 50 points — among the widest in the country.
Across the recorded series it reached a Democratic high of 46.6 points in 2016 and a Republican high of 47.5 points in 1924. Between 2020 and 2024 the district moved 14.3 points toward the Republican candidate; the 2024 margin was 28.5 points.
A population of 770,191, a 19% non-Hispanic-white share, and a median household income of $103,517 describe the district. The district's voting pattern over the last decade is most similar to that of Congressional District 29 and Congressional District 44.
The congressional districts whose fingerprint — 2000–2024 trajectory, demographics, ancestry, religion — sits closest to this one, and why.
Twin score (0–100) = weighted cosine between tier-standardized fingerprints: presidential margins 2000–2024 with 12-yr trend and elasticity, ACS income, age, education, population and race, top reported ancestries, and religious adherence — chips name the closest-shared dimensions and the widest gap. Re-weight the groups in the twins explorer.
District research tools
Open the source-auditable district brief for electoral baseline, electorate, current-cycle coverage, geography, official dates, and methodology. Open campaign intelligence report → · Browse all comparisons →
California 18th Congressional District. Akashic. https://akashic.app/cd/0618/. Accessed May 20, 2026. License: CC BY 4.0.