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Chance the Democrat wins (<0.1%)
Chance the Republican wins (>99.9%)
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.
R+30.5
Adjusted polls
R+28.4
CANTOR
R+28.5
Fundamentals
R+29.0
Experts
R+29.4
Lite
R+29.2
Classic
R+29.1
Deluxe
<0.1
<0.1
Historical adjustment
Key
More weight
Less
We've collected one poll for the Arizona 4th. 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 | Brill | Gosar | margin | likely voter | Time-line | House effects | Adjusted margin | |
Sep. 25 9/25 | OH Predictive Insights / MBQF | 370 | LV | 0.73 | 25% | 57% | R+32.0 | — | 0.1 | 1.6 | R+30.5 |
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. | ||
---|---|---|---|
ID-1 | 61 | R+7.0 | |
CA-1 | 55 | — | |
OR-2 | 51 | R+12.7 | |
WY at large | 46 | R+27.6 | |
ID-2 | 44 | R+35.0 | |
CO-4 | 44 | — | |
KS-1 | 42 | R+18.6 | |
CO-3 | 42 | R+9.0 | |
FL-1 | 40 | — | |
FL-2 | 40 | — |
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 | 3.0 | Paul Gosar has been elected to 4 terms. Congress has only a 20.1% approval rating, reducing the incumbency advantage. |
District partisanship | 15.4 | AZ-4 is 42.8 percentage points more Republican-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 Romney in 2012. |
Incumbent's margin in last election | 17.2 | Gosar won by 42.9 percentage points in 2016. |
Generic ballot | 6.6 | Democrats lead by an average of 8.6 percentage points in polls of the generic congressional ballot. |
Fundraising | 0.6 | As of Oct. 17, Gosar had raised $334,000 in individual contributions (53% of all such contributions to the major-party candidates); David Brill had raised $303,000 (47%). |
Incumbent's voting record in Congress | 1.9 | Gosar has voted with Republicans 86% 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 | Brill has never held elected office. |
Scandals | 0.0 | Neither candidate is involved in a scandal. |
Total | R+28.5 |
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 | R+29.4 | R+28.7 | |
Inside Elections | R+29.4 | R+28.5 | |
Sabato's Crystal Ball | R+29.4 | R+29.8 | |
Average | R+29.4 | R+29.0 |
Nate Silver explains the methodology behind our 2018 midterms forecast. Read more …
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