IA-3 · House

The district, in brief

Iowa's 3rd district is based in southwestern Iowa and includes the city of Des Moines. The facts record no redraw for this cycle; the lines are the map first used in 2022.

The incumbent is Republican Zach Nunn, re-elected with 51.8% of the vote in 2024, who was unopposed in his primary with 100.0%. The Democratic nominee is Sarah Trone Garriott, state senator from the 14th district since 2021, who was also unopposed with 100.0% after Jennifer Konfrst, minority leader of the Iowa House from 2021 to 2025, withdrew and endorsed her; Xavier Carrigan was disqualified and state representative Austin Baeth declined. A Libertarian, Marco Battaglia, was disqualified. As of June 30, 2026 Nunn had raised $4,869,249 with $3,568,369 on hand; Trone Garriott had raised $5,293,773 with $3,859,683 on hand.

Decision Desk HQ calls the seat Flip (July 14, 2026); the Cook Political Report (January 15, 2026), Inside Elections (August 6, 2026) and Sabato's Crystal Ball (October 2, 2025) have Tossup; Silver Bulletin is listed with an August 20, 2026 date but no ranking. One head-to-head poll is recorded: Ragnar Research Partners, a Republican firm (March 12–14, 2026, 400 likely voters), had Nunn 48%, Trone Garriott 42%, 10% undecided. Earlier, Public Policy Polling (September 17–18, 2025) had Nunn and Konfrst tied at 44%, and generic-ballot tests had Ragnar at Republican 44%, Democrat 43% and Change Research (October 23–27, 2025) at Democrat 45%, Republican 42%.

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

Not in the source: The Silver Bulletin row in the predictions table carries a date but no ranking.; The polls are on Wikipedia but the model's basis says no district polls; only one tests the actual nominees.; The text gives no presidential result for the district; only the facts carry a presidential baseline.; The Endorsements and Post-primary endorsements sections are empty.; facts.candidates marks no candidate as incumbent; the text does.

Read from the district's section of Wikipedia's state page (CC BY-SA), archived as e7db07292d11; 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

Zachary Nunn (Republican), in this chamber since 2023, 2 terms. Committees: House Committee on Agriculture; House Committee on Financial Services; House Select Committee on the Strategic Competition Between the United States and the Chinese Communist Party.

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

A shift of 1.2 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?

Of about 536,018 adults 25 and over. In 2020 the district voted 49.8% Democratic (two-party) for president. With the same preferences and a 2022-style midterm turnout, it would vote 50.2% Democratic: the midterm electorate alone moves the margin 0.8 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

FEC bulk candidate summaries through June 30, 2026; $28,797 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

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 -11.3 to +16.8 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: total outside/party money: 4.8 pts toward the Democrat; experience gap (-2 levels, D minus R): 2.5 pts toward the Republican; 2024 presidential lean (R+3.0): 0.9 pts toward the Democrat; religion: mainline (12.8%): 0.5 pts toward the Democrat; unemployment rate (3.9%): 0.4 pts toward the Democrat.

How sure is it, and of what?

Total sd 8.55 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 0b33151b-a949-47f1-b845-564833a2b74d, 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).