Republicans hold this seat today (current holder); Democrats are favored: 78 in 100 that it changes hands.
Sarah Trone Garriott wins in 78 of 100 simulations.
There are no qualifying public polls yet, so the forecast leans on fundamentals; partisan lean, the national environment and incumbency point to Sarah Trone Garriott +4.3.
Every simulated outcome, grouped in 2-point steps. Projected margin Garriott +4.3; 80 in 100 fall between Nunn +2.9 and Garriott +11.6.
Zachary Martin Nunn is an American politician and United States Air Force officer who has served as the U.S. representative for Iowa's 3rd congressional district since 2023. Wikipedia
Sarah Trone Garriott is an American politician and minister serving as a member of the Iowa Senate from the 14th district since 2021. A member of the Democratic Party, she represents part of Dallas County in the Des Moines area and served previously as Senate minority whip. Wikipedia
Ballot list and short bios from Wikipedia (CC BY-SA); websites from Wikidata; fundraising from the FEC (cycle-to-date, latest report).
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No public polls have tested Sarah Trone Garriott against Zach Nunn yet.
No polls of this matchup yet, so there is no polling average. The forecast relies on fundamentals.
How this race’s odds have moved as polls and the national environment changed.
Out of 100. Today: Garriott 78, Nunn 22.
The model blends each estimate by how much to trust it right now. Polls get 0% of the weight, 15 days out.
| Polling average (after adjustments) | — | no polls |
| Partisan lean (Cook PVI, 2026 lines) | R+2.0 | roughly 4 points of margin vs. the nation |
| National environment | D+9.6 | generic ballot + presidential approval |
| Incumbent’s track record | Garriott +2.4 | In 2024 they ran 4.7 pts more Democratic than the state’s lean predicted; half carries over (max 10) |
| Incumbency | Nunn +3.6 | incumbent’s side |
| Fundamentals estimate | Garriott +4.3 | ±6 typical error |
| Expert ratings (average) | — | used only in the “+ Expert ratings” version |
| Forecast | Garriott +4.3 | ±5.7 standard deviation, including 2.3 for movement before Election Day |
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