Top-two primary
All candidates run in one primary regardless of party and the two with the most votes advance, so two candidates of the same party can meet in November. The forecast then marks the seat as safe for that party.
California › U.S. House of Representatives · November 3, 2026 · Updated Oct 16, 2026
California's 21st District
Top twoCosta is very likely to win: Costa wins in more than 99 of every 100 simulations.
Costa (D)
99%
chance of winning
Kirkland (R)
1%
- Average margin
- D+19.0
- 80% of outcomes
- D+10 to D+29
- Partisan lean
- D+10
- Polls
- No pollsmodel only
Costa is clearly favored to win: Costa wins in 19 of every 20 simulations.
Costa (D)
94%
chance of winning
Kirkland (R)
6%
- Average margin
- D+15.8
- 80% of outcomes
- D+4 to D+28
- Partisan lean
- D+10
- Polls
- No pollsmodel only
How this race is decided
Range of outcomes
Final margin across our simulations; the white dashes mark the middle 80%.
The candidates
DemocraticIncumbent
Jim Costa
Incumbent U.S. representative
- Experience
- Statewide office or Congress
- Raised
- $1.3M
- From individuals
- $527.7K
- Spent
- $608.7K
- Cash on hand
- $938.8K
Money: FEC, through Jun 30, 2026.
Republican
Kyle Kirkland
Casino owner and candidate for the 20th district in 2024
- Experience
- No elected office
- Raised
- $339K
- From individuals
- $211.5K
- Spent
- $321K
- Cash on hand
- $17.9K
Money: FEC, through Jun 30, 2026.
What goes into the forecast
Every ingredient's estimate of the final margin.
- National environment
- D+9.5Election Day forecast; federal races run in it
- Swing reaching this office
- 78%Of a shift in the environment, from past House races since 2016
- Pacific adjustment
- −1.2How House races in the region have run against lean and environment lately
Each estimate is a margin before national and statewide uncertainty is simulated. Horizon blends polls, fundamentals and a little of the similar-places estimate, weighting each by how precise it is; Pulse uses polls and similar places only.
Fundamentals inputs
| Incumbency (+1 D, −1 R) | 1 |
| Fundraising edge (log ratio of individual money) | 0.84 |
| Elected-experience edge | 1 |
| First-term incumbent | 0 |
| Seat's last result vs. expectation | 0 |
| Incumbent's last result vs. expectation | 0 |
Polls
No public polls of this race. The forecast relies on fundamentals and on polling of similar places.
The district
Lean D+10: how much more Democratic or Republican than the nation it votes for president.
Presidential vote
Precinct results re-aggregated to the current district lines.
Who lives here
- Population
- 745,643
- People per km²
- 441
- Adults with a B.A.+
- 18%
- White, no degree
- 17%of adults
- White 20%
- Hispanic 63%
- Black 4%
- Asian 10%
- Other / multiracial 3%
American Community Survey 2020–2024, aggregated from census tracts.
Past results
Results in the same-numbered district; earlier elections may have used different lines.
2024 Earlier district lines
195,261 votes · D+5.2✓ Jim Costa (D)52.6%
Michael Maher (R)47.4%
2024 President Vote in this district
195,676 two-party votes · D+6.2 · D+7.7 vs. the nation✓ Kamala Harris (D)53.1%
Donald Trump (R)46.9%
2022 Earlier district lines
125,970 votes · D+8.2✓ Jim Costa (D)54.1%
Michael Maher (R)45.9%
2020 Earlier district lines
170,334 votes · R+0.9✓ David G Valadao (R)50.4%
Tj Cox (D)49.6%
2020 President Vote in this district
222,709 two-party votes · D+22.1 · D+17.6 vs. the nation✓ Joe Biden (D)61.0%
Donald Trump (R)39.0%
2018 Earlier district lines
113,616 votes · D+0.8✓ Tj Cox (D)50.4%
David G Valadao (R)49.6%
2016 Earlier district lines
132,029 votes · R+13.4✓ David G Valadao (R)56.7%
Emilio Huerta (D)43.3%
2016 President Vote in this district
165,912 two-party votes · D+23.4 · D+21.1 vs. the nation✓ Hillary Clinton (D)61.7%
Donald Trump (R)38.3%