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Illinois 6th
Toss-up
1 in 2
Chance the Democrat wins (48.6%)
1 in 2
Chance the Republican wins (51.4%)
Forecasted turnout
Partisan lean
# How the forecast has changed
We'll be updating our forecasts every time new data is available, every day through Nov. 6.
Chance of winning
Popular vote share
# What goes into the classic forecast in the Illinois 6th
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+1.0
Adjusted polls
D+0.8
CANTOR
R+2.0
Fundamentals
D+6.3
Experts
D+1.0
Lite
R+0.2
Classic
D+2.0
Deluxe
<0.1
<0.1
Historical adjustment
Key
More weight
Less
#Latest polls
We've collected six polls for the Illinois 6th. 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 | Casten | Roskam | margin | likely voter | Time-line | House effects | Adjusted margin | |
Oct. 20-26 10/20-26 | Siena College/New York Times | 497 | LV | 1.53 | 46% | 44% | D+1.2 | — |  <0.1 | 0.3 | D+1.0 |
Sep. 29-Oct. 1 9/29-10/1 | Garin-Hart-Yang Research Group D | 400 | LV | 0.28 | 49% | 44% | D+5.0 | — | <0.1 | 3.1 | D+1.9 |
Sep. 8-10 9/8-10 | Garin-Hart-Yang Research Group D | 402 | LV | 0.04 | 47% | 44% | D+3.0 | — | 0.1 | 3.1 | R+0.3 |
Sep. 4-6 9/4-6 | Siena College/New York Times | 512 | LV | 0.02 | 44% | 45% | R+1.0 | — | 0.1 | 0.3 | R+1.4 |
Jul. 23-25 7/23-25 | Victory Research | 600 | LV | 0.02 | 37% | 44% | R+6.9 | — | 0.6 | 2.3 | R+4.0 |
Apr. 21-23 4/21-23 | Garin-Hart-Yang Research Group D | 401 | LV | 0.00 | 44% | 45% | R+1.0 | — | 1.1 | 3.1 | R+3.0 |
Weighted averageD+1.0
Key
A = adults
RV = Registered voters
V = voters
LV = likely voters
R
D
= partisan poll
Our latest coverage
#Similar districts and CANTOR
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.
Districts most similar to the Illinois 6th
| Sim. score | Polling avg. | ||
|---|---|---|---|
| MI-11 | 70 | D+4.6 | |
| IL-14 | 62 | D+4.1 | |
| MN-3 | 61 | D+7.1 | |
| NJ-5 | 57 | D+12.0 | |
| PA-1 | 55 | D+0.5 | |
| NJ-7 | 55 | D+5.4 | |
| KS-3 | 54 | D+9.8 | |
| NJ-11 | 53 | D+8.0 | |
| NY-3 | 51 | — | |
| PA-6 | 51 | — |
#The “fundamentals”
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 | 3.2 | Peter J. Roskam has been elected to 6 terms. Congress has only a 20.1% approval rating, reducing the incumbency advantage. |
| District partisanship | 0.7 | IL-6 is 2.0 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 Clinton in 2016 and Romney in 2012. |
| Incumbent's margin in last election | 7.2 | Roskam won by 18.4 percentage points in 2016. |
| Generic ballot | 7.0 | Democrats lead by an average of 8.6 percentage points in polls of the generic congressional ballot. |
| Fundraising | 1.6 | As of Oct. 17, Sean Casten had raised $4,352,000 in individual contributions (56% of all such contributions to the major-party candidates); Roskam had raised $3,407,000 (44%). |
| Incumbent's voting record in Congress | 1.3 | Roskam has voted with Republicans 83% of the time in roll-call votes in recent sessions of Congress. |
| Challenger experience | 0.7 | Casten has never held elected office. |
| Scandals | 0.0 | Neither candidate is involved in a scandal. |
| Total | R+2.0 |
#Expert ratings
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+6.7 | D+7.4 | |
| Inside Elections | D+4.4 | D+5.3 | |
| Sabato's Crystal Ball | D+6.7 | D+6.3 | |
| Average | D+5.9 | D+6.3 | |
How this forecast works
Nate Silver explains the methodology behind our 2018 midterms forecast. Read more …
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