Iowa’s 1st District
Incumbent: Mariannette Miller-Meeks, currently Republican.
The average over time
Each poll is first shifted by its sponsor's and its pollster's measured lean, then weighted by recency and track record. Sample size gets no weight: in 2,000-plus past races it predicted nothing about accuracy. Why.
What the fundamentals say
A regression on past House races, fit without looking at this year. The national environment term uses the generic ballot after its historical correction (D+5.3).
The one poll in the average
“Share” is how much of today’s average each poll supplies. It depends on recency, the pollster’s record, whether the poll screens for likely voters, and how many other polls the same firm has in the race. It does not depend on sample size.
| Dates | Pollster | Sample | Bohannan | Miller-Meeks | As published | Adjusted | Share of average | |
|---|---|---|---|---|---|---|---|---|
| Jul 13–16 | The Bullfinch Group for Independent Center | Independent Leadership Council | 705 LV | 40 | 35 | D+5 | D+4.5 moved 0.5 toward R | 100% | source |
LV: likely voters. RV: registered voters. A: all adults. “Adjusted” is the published margin after removing the sponsor shift and the pollster’s measured house effect; the small print says how far that moved the poll. Dem.-aligned and Rep.-aligned mark polls paid for by a party, a campaign, or an allied group, or taken by a firm whose published work is mostly for one side. They are shifted by the average lean of such polls, then counted at full weight.