U.S. House · Proposition 50 Lines

Congressional District 10

Mark DeSaulnier (Democratic), re-elected in 2026

Who represents this district

Mark DeSaulnier (Democratic) was re-elected on November 3, 2026.

Counties and cities

Counties: Alameda (partial), Contra Costa (partial)

Principal cities and communities:

ConcordSan RamonWalnut CreekBrentwoodDanvillePleasant HillMartinezLafayette

Voter registration

Registered voters	Democratic	Republican	Other
500,543	48.26%	22.11%	29.63%

Secretary of State Report of Registration, September 4, 2026. Other covers every registrant not registered Democratic or Republican.

Capitol Daybook Research

Research access

The full district files are available to Capitol Daybook Research clients. A Capitol Daybook subscription does not include research access.

The full district file carries registration trends across the recent Secretary of State reports, 2024 presidential results computed on the current district lines, 2026 campaign finance totals with independent expenditures, and CSV downloads of the district tables.

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Registration: California Secretary of State, Report of Registration, September 4, 2026. 2026 results: Associated Press calls for U.S. House races; state legislative results compiled from Ballotpedia and JoinCalifornia against semi-official returns. District lines: congressional districts are the Proposition 50 (AB 604) map; State Senate and Assembly districts are the 2021 Citizens Redistricting Commission maps.