MO-3 · House
election-day forecast · ground-up model · as of 2026-10-02
The district, in brief
Missouri's 3rd district covers all of St. Charles County and extends west to take in most of Columbia and north to Mexico and a section of Hannibal. The lines are the map first used in 2022 and are not redrawn for this cycle.
The incumbent is Republican Bob Onder, elected with 61.3% of the vote in 2024. He won his primary 66.3% to 33.7% over accountant John G. Fraser. The Democratic nominee is Bethany Mann, a technology specialist who was the party's nominee for the seat in 2022 and 2024; she took 69.1% in her primary over videographer Tommy Holstein (17.7%) and Paul Wilson (13.2%), who withdrew but remained on the ballot. Libertarian Jim Higgins is also standing. As of July 15, 2026 Onder had raised $950,350 with $471,459 on hand; Mann had raised $43,339 with $2,776 on hand.
The facts record Republican two-party margins of 26.93 points in 2024 and 30.22 in 2022, when Blaine Luetkemeyer held the seat. Every rater listed calls the seat R: Decision Desk HQ (August 12, 2026), the Cook Political Report (February 6, 2025), Inside Elections (March 7, 2025) and Sabato's Crystal Ball (July 15, 2025).
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 Republican Bob Onder, who was elected with 61.3% of the vote in 2024.
The incumbent is Republican Bob Onder
Bethany Mann, technology specialist and nominee for this district in 2022 and 2024
Bob Onder, incumbent U.S. representative
Bethany Mann, technology specialist and nominee for this district in 2022 and 2024
Bob Onder, incumbent U.S. representative
who was elected with 61.3% of the vote in 2024
candidate: Bob Onder (incumbent) party: Republican Party (United States) votes: 66,784 percentage: 66.3
Decision Desk HQ R August 12, 2026 The Cook Political Report R February 6, 2025
Bob Onder (R) $950,350 $629,335 $471,459
Paul Wilson, dentist anesthesiologist (remained on ballot)
Jim Higgins, computer systems analyst and perennial candidate
Not in the source: The text gives no presidential vote shares for the district.; Ratings are given only as 'R' with no Lean/Likely/Safe gradation.; No district polls in the text, and the model's basis says none.; Endorsement sections are empty.
Read from the district's section of Wikipedia's state page (CC BY-SA), archived as 74160a6d1921; 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
Robert F. Onder, Jr. (Republican), in this chamber since 2025, 1 term. Committees: House Committee on Transportation and Infrastructure; House Committee on the Judiciary; House Committee on Education and Workforce.
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 | R+33.6 | R+27.7 | R+28.7 |
A shift of 4.9 points toward the Democrats 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 | 58% | 60% / 46% | 50% | 15% |
| White, degree | 31% | 82% / 71% | 41% | 59% |
| Black | 4% | 68% / 50% | 4% | 91% |
| Hispanic | 2% | 41% / 27% | 1% | 57% |
| Asian | 2% | 28% / 15% | 1% | 59% |
| Other / multiracial | 3% | 64% / 52% | 3% | 53% |
Of about 521,459 adults 25 and over. In 2020 the district voted 36.6% Democratic (two-party) for president. With the same preferences and a 2022-style midterm turnout, it would vote 37.7% Democratic: the midterm electorate alone moves the margin 2.1 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 |
|---|---|---|---|---|---|---|
| Onder, Robert For Jr. (REP) incumbent | $950,350 | $471,459 | 39% | 0% | $8 | $1,662 |
| Onder Jr, Robert Frank (REP) challenger · not on our roster | $950,350 | $471,459 | 39% | 0% | $0 | $0 |
| Mann, Bethany (DEM) challenger | $43,339 | $2,776 | 0% | 0% | $0 | $0 |
| Fraser, John G (REP) challenger · not on our roster | $17,196 | $3,783 | 0% | 79% | $0 | $0 |
| Holstein, Tommy (DEM) challenger · not on our roster | $10,095 | $2,470 | 0% | 12% | $0 | $0 |
| Wilson, Paul (DEM) challenger · not on our roster | $4,162 | $0 | 0% | 62% | $0 | $0 |
FEC bulk candidate summaries through August 04, 2026; $1,670 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+ | 35.2% | 34.9% | +0.3 pts |
| White, non-Hispanic | 85.2% | 58.2% | +27.0 pts |
| Black, non-Hispanic | 4.7% | 12.0% | -7.3 pts |
| Hispanic or Latino | 3.5% | 19.0% | -15.6 pts |
| Asian, non-Hispanic | 2.2% | 5.8% | -3.6 pts |
| Foreign-born | 3.5% | 13.9% | -10.4 pts |
| Median age | 39.2 | 39.2 | -0.0 |
| Median household income | $80,027 | $84,362 | $-4,335 |
| Median home value | $249,300 | $379,737 | $-130,437 |
| Owner-occupied homes | 75.0% | 65.1% | +9.9 pts |
| Unemployment, July 2026 (BLS county data) | 3.5% | 4.4% | -0.8 pts |
| Change in unemployment, past 12 months | -0.4 pts | — | — |
| Change since the last election (24 months) | -0.3 pts | — | — |
| Unemployment (ACS) | 3.4% | 5.2% | -1.8 pts |
| Federal government workers | 1.9% | 2.6% | -0.8 pts |
| Work from home | 11.2% | 13.5% | -2.2 pts |
| Households on SNAP | 6.0% | 11.8% | -5.7 pts |
| Households with Social Security income | 32.4% | 31.2% | +1.2 pts |
| Households with public assistance income | 1.4% | 2.7% | -1.3 pts |
| Moved in from another state, past year | 2.0% | 2.3% | -0.3 pts |
| Gini index | 0.40 | 0.44 | -0.04 |
| Per-capita personal income (BEA), 2024 | $63,031 | $73,248 | $-10,217 |
| Per-capita income growth since 2019, nominal, 2024 | 31.3% | 32.0% | -0.7 pts |
| Government and other transfers, share of income, 2024 | 19.5% | 19.6% | -0.1 pts |
| Social Security, share of income, 2022 | 7.1% | 5.8% | +1.2 pts |
| Medicare, share of income, 2022 | 4.8% | 4.5% | +0.3 pts |
| Medicaid, share of income, 2022 | 3.0% | 4.0% | -1.0 pts |
| SNAP, share of income, 2022 | 0.2% | 0.6% | -0.4 pts |
| Earned Income Tax Credit, share of income, 2022 | 0.3% | 0.4% | -0.1 pts |
| Veterans' benefits, share of income, 2022 | 0.9% | 0.9% | -0.0 pts |
| Federal civilian jobs, share of all jobs, 2022 | 0.8% | 1.3% | -0.5 pts |
| Military jobs, share of all jobs, 2022 | 0.5% | 0.9% | -0.4 pts |
ACS 5-year 2023, the Census Bureau's own tabulation of this district (118th Congress lines). 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 -34.6 to -6.6 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 (R+27.4): 12.3 pts toward the Republican; 2024 House lean (R+24.2): 4.5 pts toward the Republican; asian share (2.2%): 1.1 pts toward the Republican; experience gap (-4 levels, D minus R): 1.0 pts toward the Republican; hispanic share (3.6%): 0.5 pts toward the Democrat.
How sure is it, and of what?
Total sd 8.54 points, made of the seat's own volatility 89%, correlated polling error 11%. 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).