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Chance the Democrat wins (98.8%)
Chance the Republican wins (1.2%)
We'll be updating our forecasts every time new data is available, every day through Nov. 6.
The Classic version of our model projects a race’s outcome by taking a weighted average of polls of a district (if available), polls of similar districts (CANTOR) and non-polling factors (fundamentals). It is then reverted toward a mean based on long-term trends in midterms and presidential approval ratings.
D+13.3
Adjusted polls
D+16.2
CANTOR
D+17.5
Fundamentals
D+23.0
Experts
D+14.3
Lite
D+15.4
Classic
D+17.9
Deluxe
<0.1
<0.1
Historical adjustment
Key
More weight
Less
We've collected three polls for the Iowa 2nd. We’re adjusting poll results in three ways: Polls of registered voters or all adults are adjusted to a likely-voter basis; older polls are adjusted based on shifts in the generic congressional ballot since the poll was conducted; and polls are adjusted for house effects (the tendency for a firm’s polls to lean toward Democrats or Republicans). Polls with larger sample sizes and those conducted by higher-quality polling agencies are given more weight, as are more recent polls.
Adjustments | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
dates | pollster | sample | weight | Loebsack | Peters | margin | likely voter | Time-line | House effects | Adjusted margin | |
Oct. 29-Nov. 1 10/29-11/1 | Emerson College | 373 | LV | 1.25 | 53% | 40% | D+12.9 | — | <0.1 | 0.6 | D+13.5 |
Sep. 8-11 9/8-11 | Gravis Marketing R | 425 | A | 0.04 | 45% | 38% | D+7.0 | 1.4 | 0.2 | 2.3 | D+7.7 |
Sep. 6-8 9/6-8 | Emerson College | 250 | RV | 0.00 | 45% | 21% | D+24.7 | 0.2 | 0.2 | 0.6 | D+25.0 |
Key
A = adults
RV = Registered voters
V = voters
LV = likely voters
= partisan poll
Our district similarity scores are based on demographic, geographic and political characteristics; if two districts have a score of 100, it means they are perfectly identical. These scores inform a system we use — CANTOR, or Congressional Algorithm using Neighboring Typologies to Optimize Regression — to infer what polling would say in unpolled or lightly polled districts, given what it says in similar districts.
Sim. score | Polling avg. | ||
---|---|---|---|
IA-1 | 81 | D+8.8 | |
MI-6 | 77 | R+2.7 | |
IA-3 | 77 | D+1.6 | |
WI-3 | 73 | — | |
OH-15 | 71 | — | |
KS-2 | 69 | D+0.1 | |
MI-3 | 69 | — | |
IN-9 | 67 | R+7.6 | |
MI-7 | 67 | R+6.6 | |
IL-13 | 66 | R+5.4 |
The Classic and Deluxe versions of our model use several non-polling factors to forecast the vote share margin in each district.
Factor | Impact | Explanation |
---|---|---|
Incumbency | 3.1 | Dave Loebsack has been elected to 6 terms. Congress has only a 20.1% approval rating, reducing the incumbency advantage. |
District partisanship | 0.0 | IA-2 is 0.1 percentage points more Democratic-leaning than the country overall, based on how it has voted in recent presidential and state legislative elections. It voted for Trump in 2016 and Obama in 2012. |
Incumbent's margin in last election | 3.5 | Loebsack won by 7.6 percentage points in 2016. |
Generic ballot | 6.8 | Democrats lead by an average of 8.6 percentage points in polls of the generic congressional ballot. |
Fundraising | 6.0 | As of Oct. 17, Loebsack had raised $897,000 in individual contributions (74% of all such contributions to the major-party candidates); Christopher Peters had raised $312,000 (26%). |
Incumbent's voting record in Congress | 2.5 | Loebsack has voted with Democrats 89% of the time in roll-call votes in recent sessions of Congress. Candidates who vote with their party very frequently tend to underperform at the ballot booth, other factors held equal. |
Challenger experience | 0.7 | Peters has never held elected office. |
Scandals | 0.0 | Neither candidate is involved in a scandal. |
Total | D+17.5 |
The Deluxe version of our model calculates an implied margin for each race based on expert race ratings from The Cook Political Report, Inside Elections and Sabato's Crystal Ball; it then adjusts that margin toward its estimate of the national political environment.
Equivalent Margin | |||
---|---|---|---|
Expert | Rating | Raw | Adjusted |
Cook Political Report | D+22.6 | D+23.2 | |
Inside Elections | D+22.6 | D+23.5 | |
Sabato's Crystal Ball | D+22.6 | D+22.2 | |
Average | D+22.6 | D+23.0 |
Nate Silver explains the methodology behind our 2018 midterms forecast. Read more …
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