Montana at large

Likely R

1 in 4

Chance the Democrat wins (24.4%)

3 in 4

Chance the Republican wins (75.6%)

See the national overview

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

KEY

AVERAGE

80% CHANCE OF FALLING IN RANGE

# What goes into the

classic forecast in Montana

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+4.6
Adjusted polls
R+10.6
CANTOR
R+2.2
Fundamentals
R+8.1
Experts

R+4.6

Lite
R+4.2

Classic
R+5.5

Deluxe

<0.1
<0.1

Historical adjustment

Key

More weight

Less

#Latest polls

We've collected nine polls for Montana. 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	Williams	Gianforte	margin	likely voter	Time-line	House effects	Adjusted margin
Nov. 2-4 11/2-4	Change Research	879	LV	1.78	44%	52%	R+8.0	—	<0.1	0.6	R+8.6
Oct. 24-26 10/24-26	Gravis Marketing	782	LV	0.88	48%	48%	EVEN	—	<0.1	1.4	D+1.4
Oct. 10-18 10/10-18	University of Montana	533	LV	0.39	46%	45%	D+0.5	—	<0.1	4.9	R+4.4
Oct. 8-13 10/8-13	Montana State University Billings	471	LV	0.39	41%	44%	R+3.0	—	<0.1	0.2	R+3.2
Sep. 15-Oct. 6 9/15-10/6	MSU - Bozeman	2,079	RV	0.26	40%	48%	R+7.5	0.2	0.1	2.6	R+5.1
Sep. 19-22 9/19-22	Gravis Marketing	710	LV	0.02	42%	51%	R+9.0	—	0.1	1.4	R+7.7
Sep. 6-16 9/6-16	Benenson Strategy Group	950	LV	0.11	45%	46%	R+1.0	—	0.1	0.2	R+1.4
Aug. 13-31 8/13-31	University of Montana	466	LV	0.00	51%	38%	D+13.0	—	0.2	4.9	D+8.2
Jun. 11-13 6/11-13	Gravis Marketing	469	LV	0.00	49%	43%	D+6.0	—	0.9	1.4	D+8.3

Weighted averageR+4.6

Key

A = adults

RV = Registered voters

V = voters

LV = likely voters

= partisan poll

#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 Montana

	Sim. score	Polling avg.
WA-5	71	R+6.9
OR-2	66	R+12.7
CO-3	65	R+9.0
CA-1	61	—
WA-3	61	R+4.9
ID-1	56	R+7.0
KS-2	54	D+0.1
MN-8	54	R+12.2
OR-4	54	—
MI-7	53	R+6.6

#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	3.1	Greg Gianforte has been elected to 1 term. Congress has only a 20.1% approval rating, reducing the incumbency advantage.
District partisanship	6.3	Montana is 17.9 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. Montana has been considerably more Democratic in state legislative elections than in presidential elections.
Incumbent's margin in last election	7.1	Gianforte won by 5.6 percentage points in a special election.
Generic ballot	6.8	Democrats lead by an average of 8.6 percentage points in polls of the generic congressional ballot.
Fundraising	0.2	As of Oct. 17, Kathleen Williams had raised $3,156,000 in individual contributions (51% of all such contributions to the major-party candidates); Gianforte had raised $3,064,000 (49%).
Incumbent's voting record in Congress	1.2	Gianforte has voted with Republicans 83% of the time in roll-call votes in recent sessions of Congress.
Challenger experience	1.9	Williams has held elected office before. (So has Gianforte, but this is accounted for in our incumbency calculation.)
Scandals	4.1	Gianforte was involved in a scandal. But it developed in 2017, before the current election cycle, so our model discounts its importance.
Total	R+2.2

#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	Lean R	R+6.7	R+6.1
Inside Elections	Likely R	R+12.1	R+11.2
Sabato's Crystal Ball	Leans R	R+6.7	R+7.1
Average		R+8.5	R+8.1

How this forecast works

Nate Silver explains the methodology behind our 2018 midterms forecast. Read more …

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