CA-10 · House
election-day forecast · ground-up model · as of 2026-10-02
The district, in brief
California's 10th is on a map first used in 2026, but the text says nothing about the district's lines or how they changed, and gives no presidential result.
The incumbent is Democrat Mark DeSaulnier, re-elected with 66.5% in 2024. He led the top-two primary with 59.68%; the Republican who advanced with him is Jeff Frese, a business owner, at 12.94%, ahead of Katherine Piccinini, the district's 2024 runner-up, at 11.50%. Former state senator Steve Glazer and state senator Tim Grayson declined to run and endorsed DeSaulnier. As of May 13, 2026 DeSaulnier had raised $515,092 with $627,906 on hand; Frese reported $0 raised and $0 on hand.
Decision Desk HQ (July 14, 2026), the Cook Political Report (November 5, 2025), Inside Elections (March 7, 2025), Sabato's Crystal Ball (July 15, 2025) and The Economist (May 6, 2026) all call the seat D. No polls are listed.
A paragraph quoting a model forecast from the day this brief was written is omitted; the current forecast is at the top of this page.
The facts, each beside its sentence
The incumbent is Democrat Mark DeSaulnier, who was re-elected with 66.5% of the vote in 2024.
Mark DeSaulnier (Democratic), incumbent U.S. representative
Mark DeSaulnier (Democratic), incumbent U.S. representative
Jeff Frese (Republican), business owner
Mark DeSaulnier (Democratic), incumbent U.S. representative
Jeff Frese (Republican), business owner
who was re-elected with 66.5% of the vote in 2024
candidate: Jeff Frese votes: 28,671 percentage: 12.94
Decision Desk HQ D July 14, 2026 The Cook Political Report D November 5, 2025
Jeff Frese (R) $0 $0 $0
Katherine Piccinni (Republican), property manager and runner-up for this district in 2024 and write-in candidate in 2022
Tim Grayson (Democratic), state senator from the 9th district (2024–present) (endorsed DeSaulnier)
Not in the source: The facts mark the district as redrawn for 2026, but the text says nothing about the lines, old or new.; The text gives no presidential results for the district.; No polls of any kind are listed.; The endorsement list in the text has lost its headings, so it is unclear whom Planned Parenthood Action Fund, the Sierra Club, the California Democratic Party and the newspapers listed endorsed.; No fundraising later than May 13, 2026.
Read from the district's section of Wikipedia's state page (CC BY-SA), archived as 5cec783f78c8; written by claude-fable-5-1 (batch reader) on 2026-09-30 and checked mechanically: every quote occurs verbatim in the archived text, every number in the brief occurs in the inputs. No probability here is the reader's.
Who holds the seat now
Mark DeSaulnier (Democrat), in this chamber since 2015, 6 terms. Committees: House Committee on Transportation and Infrastructure; House Committee on Education and Workforce; House Committee on Ethics (Ranking Member).
From the congress-legislators dataset (CC0), archived as ae8cb9477c48. For a Senate race this lists both of the state's senators; the one whose term ends in the election year holds the seat on the ballot. For a House district redrawn for 2026 it is the member elected under the old lines with this number, who may be running elsewhere; the dossier above names who is running here.
How it has voted for president
| Two-party margin | 2016 | 2020 | 2024 |
|---|---|---|---|
| President | D+49.0 | D+48.0 | D+40.9 |
A shift of 8.1 points toward the Republicans from 2016 to 2024. county returns placed on the current lines by 2020 block population; MEDSL county file (2016), an MIT-licensed county file (2020, checked against certified state results) and MEDSL precinct returns (2024). For a district split across counties this is an estimate, and where the state published the exact 2024 figure for these lines, that exact figure is the one the model uses.
Who are the voters?
| Group (adults 25+) | Share of adults | Turnout 2020 / midterm | Share of a midterm electorate | Est. Democratic share, 2020 |
|---|---|---|---|---|
| White, no degree | 24% | 62% / 48% | 23% | 19% |
| White, degree | 31% | 84% / 75% | 46% | 91% |
| Black | 5% | 60% / 41% | 4% | 93% |
| Hispanic | 16% | 41% / 31% | 10% | 73% |
| Asian | 20% | 47% / 34% | 14% | 80% |
| Other / multiracial | 4% | 56% / 44% | 4% | 79% |
Of about 531,715 adults 25 and over. In 2020 the district voted 69.8% Democratic (two-party) for president. With the same preferences and a 2022-style midterm turnout, it would vote 70.8% Democratic: the midterm electorate alone moves the margin 1.9 points toward Democrats. Group shares are estimated from how results vary across the state's census tracts (ecological inference, anchored to Pew's 2020 validated-voter figures) and calibrated to this district's actual 2020 vote; turnout is the Census survey's state rate by race and national rate by education, whose state samples carry margins of several points.
Not answered here: how each group will vote in 2026. These are 2020 preferences; this profile is description, not yet an input to the forecast.
The money
| Candidate | Raised | Cash on hand | PAC share | Self-funded | Outside $ for | Outside $ against |
|---|---|---|---|---|---|---|
| Desaulnier, Mark (DEM) incumbent | $567,258 | $586,497 | 54% | 0% | $165 | $0 |
| Piccinini, Katherine (REP) challenger · not on our roster | $21,074 | $6,836 | 0% | 0% | $0 | $0 |
| Griffiths, Angela (REP) challenger · not on our roster | $11,811 | $3,911 | 0% | 1% | $0 | $0 |
| Maisler, Mitchell David (DEM) challenger · not on our roster | $10,048 | $-514 | 0% | 79% | $0 | $0 |
| Hamilton, Joshua (DEM) challenger · not on our roster | $7,486 | $1,080 | 0% | 0% | $0 | $0 |
FEC bulk candidate summaries through June 30, 2026; $165 of independent expenditures for or against these candidates this cycle (FEC Schedule E, types 24E and 24A), which is the parties' and outside groups' own revealed view of whether this seat is in play.
The district in numbers
| Measure | District | Nation | Difference |
|---|---|---|---|
| Bachelor's degree or higher, 25+ | 53.0% | 34.9% | +18.1 pts |
| White, non-Hispanic | 48.5% | 58.2% | -9.8 pts |
| Black, non-Hispanic | 4.5% | 12.0% | -7.5 pts |
| Hispanic or Latino | 19.8% | 19.0% | +0.8 pts |
| Asian, non-Hispanic | 20.3% | 5.8% | +14.6 pts |
| Foreign-born | 24.1% | 13.9% | +10.2 pts |
| Median age | 42.3 | 39.2 | 3.1 |
| Median household income | $158,026 | $84,362 | $+73,664 |
| Median home value | $1,076,975 | $379,737 | $+697,238 |
| Owner-occupied homes | 71.2% | 65.1% | +6.1 pts |
| Unemployment, July 2026 (BLS county data) | 4.8% | 4.4% | +0.4 pts |
| Change in unemployment, past 12 months | -0.4 pts | — | — |
| Change since the last election (24 months) | -0.2 pts | — | — |
| Unemployment (ACS) | 5.3% | 5.2% | +0.1 pts |
| Federal government workers | 1.7% | 2.6% | -0.9 pts |
| Work from home | 23.0% | 13.5% | +9.5 pts |
| Households on SNAP | 5.1% | 11.8% | -6.6 pts |
| Households with Social Security income | 30.1% | 31.2% | -1.1 pts |
| Households with public assistance income | 2.3% | 2.7% | -0.3 pts |
| Moved in from another state, past year | 1.2% | 2.3% | -1.1 pts |
| Gini index | 0.40 | 0.44 | -0.04 |
| Per-capita personal income (BEA), 2024 | $108,567 | $73,248 | $+35,319 |
| Per-capita income growth since 2019, nominal, 2024 | 35.2% | 32.0% | +3.2 pts |
| Government and other transfers, share of income, 2024 | 12.4% | 19.6% | -7.1 pts |
| Social Security, share of income, 2022 | 3.5% | 5.8% | -2.3 pts |
| Medicare, share of income, 2022 | 2.8% | 4.5% | -1.7 pts |
| Medicaid, share of income, 2022 | 2.6% | 4.0% | -1.3 pts |
| SNAP, share of income, 2022 | 0.3% | 0.6% | -0.3 pts |
| Earned Income Tax Credit, share of income, 2022 | 0.1% | 0.4% | -0.2 pts |
| Veterans' benefits, share of income, 2022 | 0.3% | 0.9% | -0.6 pts |
| Federal civilian jobs, share of all jobs, 2022 | 0.8% | 1.3% | -0.5 pts |
| Military jobs, share of all jobs, 2022 | 0.3% | 0.9% | -0.6 pts |
ACS 5-year 2023, assembled from census tracts by the 2020 population of their blocks inside the current lines, because the Bureau has not tabulated these lines; medians are population-weighted means of tract medians. Unemployment is the BLS county series placed on the district by block population, not seasonally adjusted, so changes are same-month comparisons. Income, transfers and jobs are BEA county accounts placed the same way, compared with the average district. Every other figure is a named column of a named table in the Bureau's summary file, archived before it was read. This is what a reader knows about a district before looking at a poll; the model does not yet use it, and whether it should is a registered question.
Who is favoured, and by how much?
The 90% interval runs from +27.0 to +57.0 points, D-R. It is wide because this district has never been polled.
What is this built on?
A model trained on every contested House race 2012-2024 predicts this district's lean from its own record: presidential and House results on the current lines, incumbency, both candidates' prior offices, outside and party money before 1 October, demographics and public-assistance shares from the Census release before the election, local unemployment and income, and religious tradition. The national margin comes from presidential approval, the economy, the midterm penalty and the generic ballot corrected for its measured lean. Draws share national and state errors, so the seat total and this district come from the same simulation.
Not answered here: district polls, which are not yet folded in.
Why does the model say this?
Each figure is how far this district's predicted lean moves when that one feature is set to the typical value across 2026 districts, everything else held: 2024 presidential lean (D+36.2): 28.8 pts toward the Democrat; experience gap (+4 levels, D minus R): 12.8 pts toward the Democrat; 2024 House lean: 10.8 pts toward the Democrat; PAC money balance: 9.1 pts toward the Democrat; 2022 House lean: 1.9 pts toward the Democrat.
How sure is it, and of what?
Total sd 9.15 points, made of the seat's own volatility 92%, correlated polling error 8%. The decomposition is stored with the forecast rather than reconstructed, so a probability whose dominant input is a placeholder is visibly that.
Not answered here: a nowcast. 'If ballots were cast today' needs something that observes today, and for a House district nothing does. Publishing the election-day figure under both labels would make one forecast look like two.
How was this number made?
Run 6f211e6f-2bdc-4dda-8f72-81fc628dab0b, house_district_prior/0.2.0, as of 2026-10-02. Promoted by a pre-registered gate: on 2016-2022 its Brier score was 0.036 against 0.049 for the previous method, and on a single 2024 run 0.023 against 0.032 (experiments/district_gate_result.md, with an independent review).