Election 2018

Pennsylvania 17th

Solid D

19 in 20

Chance the Democrat wins (95.7%)

1 in 20

Chance the Republican wins (4.3%)

us_map2See the national overview
Forecasted turnout
Partisan lean

# What goes into the
icon_classic_2
classic forecast in the Pennsylvania 17th

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+12.5

    Adjusted polls

  • D+5.9

    CANTOR

  • D+10.1

    Fundamentals

  • D+10.7

    Experts

  • D+9.6

    icon_lite_2

    Lite

  • D+10.8

    icon_classic_2

    Classic

  • D+10.8

    icon_deluxe_2

    Deluxe

  • <0.1

  • <0.1

Historical adjustment

Key

More weight

Less

#Latest polls

We've collected two polls for the Pennsylvania 17th. 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
datespollstersampleweight
Lamb
Rothfus
marginlikely voterTime-lineHouse effects Adjusted margin
Oct. 5-8
10/5-8
Monmouth University354LV
1.04
54%42%D+12.7— <0.1 0.2 D+12.5
Jul. 19-22
7/19-22
Monmouth University355LV
0.00
54%39%D+14.3— 0.6 0.2 D+14.7
Weighted averageD+12.5

Key

A = adults

RV = Registered voters

V = voters

LV = likely voters

R
D

= partisan poll

Partisanship is determined by who sponsors the poll, rather than who conducts it. Polls are considered partisan if they’re conducted on behalf of a candidate, party, campaign committee, or PAC, super PAC, 501(c)(4), 501(c)(5) or 501(c)(6) organization that conducts a large majority of its political activity on behalf of one political party.

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#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 Pennsylvania 17th
Sim. score Polling avg.
PA-178D+0.5
OH-1670R+5.1
PA-768D+7.8
OH-1467—
MI-866D+2.6
NJ-365D+0.9
MI-1163D+4.6
PA-662—
PA-1062R+3.0
NH-161D+7.2

#The “fundamentals”

The Classic and Deluxe versions of our model use several non-polling factors to forecast the vote share margin in each district.

FactorImpactExplanation
Incumbency
1.3
 Conor Lamb has been elected to 1 term and Keith J. Rothfus has been elected to 3 terms. Congress has only a 20.1% approval rating, reducing the incumbency advantage. Pennsylvania underwent redistricting; there is 20% overlap between Lamb's old and new district and 55% overlap between Rothfus's old and new district.
District partisanship
2.1
 PA-17 is 5.8 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
2.4
 Lamb won by 0.3 percentage points in a special election. Rothfus won by 23.5 percentage points in 2016 in an open-seat race. However, Pennsylvania has since undergone redistricting. Lamb's district is now considerably more Democratic. Rothfus's district is now considerably more Democratic.
Generic ballot
7.0
 Democrats lead by an average of 8.6 percentage points in polls of the generic congressional ballot.
Fundraising
2.7
 As of Oct. 17, Lamb had raised $2,089,000 in individual contributions (61% of all such contributions to the major-party candidates); Rothfus had raised $1,364,000 (39%).
Incumbent's voting record in Congress
1.4
 Lamb has voted with Democrats 73% of the time and Rothfus 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.
Candidate experience
0.0
 As incubents, both Lamb and Rothfus have previously held elected office.
Scandals
0.0
 Neither candidate is involved in a scandal.
Total
D+10.1

#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
ExpertRatingRaw Adjusted
Cook Political Report
Likely D
D+12.1D+12.7
Inside Elections
Lean D
D+6.7D+7.6
Sabato's Crystal Ball
Likely D
D+12.1D+11.7
AverageD+10.3D+10.7

How this forecast works

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

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