Last updated October 20, 2017 01:56:01 PM

Who’s ahead in the race for control of the United States House of Representatives?

How does this work?


Chance of Winning a House Majority

Dem. Chance 45.1% Rep. Chance 54.9%


Fullscreen map here

Odds Over Time

Popular Vote

Popular vote percentage based on an average of generic ballot polls:

Dem. Vote: 42.1% Rep. Vote: 35.8% Und./Other: 22.1%

Two-party projection of election day using generic ballot polls.

Dem. Vote: 54.2% Rep. Vote: 45.8%

Seats

Median number of Democratic seats in our simulations (NOTE this may be more/less than the strict prediction of seats in the Seat Projections section below, for reasons explained here):

Dem. Seats: 215 Rep. Seats: 220



Popular Vote Forecast


In my projection of the two-party election day vote share, based on polls of the generic ballot, The Democratic Party is ahead, earning 54.2% of the two-party vote share on average. The margin of error is roughly 4.1% points, meaning the Democrats could earn as little as 50.1% or as much as 58.3% of the vote. Below are the generic congressional ballot polls used to make that projection:

Table 1: Polls of the Generic Congressional Ballot
Democrat Republican Date Pollster
41 33 2017-10-16 YouGov/Economist
42 37 2017-10-16 Politico/Morning Consult
51 37 2017-10-15 CNN
40 33 2017-10-10 YouGov/Economist
43 37 2017-10-09 Politico/Morning Consult
39 32 2017-10-03 YouGov/Economist
41 39 2017-10-01 Politico/Morning Consult
40 34 2017-09-26 YouGov/Economist
48 37 2017-09-25 PPP (D)
42 38 2017-09-24 Politico/Morning Consult
49 43 2017-09-20 CNN
39 33 2017-09-19 YouGov/Economist
43 37 2017-09-17 Politico/Morning Consult
40 31 2017-09-12 YouGov/Economist
40 37 2017-09-11 Politico/Morning Consult
39 33 2017-09-05 YouGov/Economist
43 38 2017-09-03 Politico/Morning Consult
40 32 2017-08-29 YouGov/Economist
40 36 2017-08-28 Politico/Morning Consult
39 33 2017-08-22 YouGov/Economist
49 35 2017-08-21 PPP (D)
41 36 2017-08-19 Politico/Morning Consult
46 40 2017-08-17 GWU/Battleground
41 33 2017-08-15 YouGov/Economist
40 38 2017-08-14 Politico/Morning Consult
47 40 2017-08-12 Marist
39 34 2017-08-08 YouGov/Economist
51 42 2017-08-06 CNN
43 36 2017-08-06 Politico/Morning Consult
39 34 2017-08-01 YouGov/Economist
44 37 2017-07-29 Politico/Morning Consult
40 34 2017-07-25 YouGov/Economist
40 40 2017-07-24 Politico/Morning Consult
40 34 2017-07-18 YouGov/Economist
50 40 2017-07-17 PPP (D)
42 40 2017-07-15 Politico/Morning Consult
39 32 2017-07-11 YouGov/Economist
43 40 2017-07-09 Politico/Morning Consult
37 35 2017-07-04 YouGov/Economist
43 39 2017-06-30 Politico/Morning Consult
47 41 2017-06-27 FOX
41 35 2017-06-27 YouGov/Economist
48 38 2017-06-25 NPR/PBS NewsHour/Marist
42 40 2017-06-24 Politico/Morning Consult
38 35 2017-06-20 YouGov/Economist
43 37 2017-06-19 Politico/Morning Consult
38 36 2017-06-13 YouGov/Economist
42 39 2017-06-12 Politico/Morning Consult
50 40 2017-06-11 PPP (D)
41 37 2017-06-06 YouGov/Economist
42 39 2017-06-02 Politico/Morning Consult
39 33 2017-05-30 YouGov/Economist
43 39 2017-05-30 Politico/Morning Consult
38 36 2017-05-23 YouGov/Economist
41 37 2017-05-22 Politico/Morning Consult
40 33 2017-05-16 YouGov/Economist
42 35 2017-05-14 Politico/Morning Consult
49 38 2017-05-14 PPP (D)
42 37 2017-05-11 Politico/Morning Consult
40 35 2017-05-09 YouGov/Economist
42 36 2017-05-06 Politico/Morning Consult
38 35 2017-05-02 YouGov/Economist
41 41 2017-04-30 Politico/Morning Consult
47 42 2017-04-25 FOX
39 34 2017-04-25 YouGov/Economist
50 41 2017-04-25 CNN
40 44 2017-04-24 Politico/Morning Consult
47 42 2017-04-20 Gravis Marketing/Orlando Political Observer
47 41 2017-04-18 PPP (D)
38 32 2017-04-18 YouGov/Economist
40 40 2017-04-15 Politico/Morning Consult
45 38 2017-04-12 McClatchy/Marist
40 37 2017-04-11 YouGov/Economist
43 40 2017-04-09 Politico/Morning Consult
41 39 2017-04-01 Politico/Morning Consult
48 43 2017-03-28 PPP (D)
47 38 2017-03-27 McClatchy/Marist
46 41 2017-03-12 PPP (D)
46 43 2017-02-22 PPP (D)
49 41 2017-02-08 PPP (D)
45 42 2017-01-31 PPP (D)
48 40 2017-01-24 PPP (D)


But, because Democrats are clustered in cities and face harsh gerrymanders, they aren’t expected to win an equivalent share of the seats in Congress. What does electoral geography tell us about the actual outcome?


Seat Forecast


Simulated Seats Over Time

Democrats earn a median of 215 seats in our simulations of the 2018 midterms. This may differ from the strict predictions below because of the larger number of Lean Republican seats than Lean Democratic seats in the current Congress. Effectively we are saying that the below number is an ideal estimate, meant to give you context as to which seats are competitive, but that we expect Democrats to overperform expectations based on the assessment of our error in past predictions.


Individual Seat Projections

Using the average vote share for each district over all of our simulations, we can identify both the districts that have the best chance of flipping parties and the chance that that happens.

Democrats: 209
Republicans: 226

Democrats are likely to pick up 16 seats on November 6, 2018. Republicans are favored to gain 1 seat, for a net gain of 15 seats for the Democratic Party.

Seats Likely to Flip Parties in 2018
District Dem 2016/14 (%) Clinton (%) Forecast Dem 2018 (%) Dem Win Prob.
1 CA-10 48.3 51.6 51.7 63
2 CA-21 43.3 58.2 52.3 68
3 CA-25 46.9 53.6 51.9 65
4 CA-39 42.8 54.6 50.5 54
5 CA-49 49.7 54 53.3 75
6 CO-06 45.6 54.9 51.9 64
7 FL-26 43.7 58.3 52.5 69
8 FL-27 45.1 60.1 63.7 99
9 MI-11 43.2 47.7 51.6 61
10 MN-01 50.4 41.9 46 25
11 MN-02 49 49.3 50.3 52
12 MN-03 43.1 55.1 50.9 57
13 NE-02 49.4 48.8 50.2 52
14 PA-15 39.4 46 50 50
15 TX-23 49.3 51.8 52.2 67
16 VA-10 47.1 55.3 52.7 71
17 WA-08 39.8 51.6 55.5 82
Forecasts for all House races on the bottom of the screen


Who’s Vulnerable?

The graph below stacks each House seat on top of eachother above the percentage share of the vote I forecast for the Democratic candidate in the district. The gray shaded area represents a 5% margin of error — roughly what we expect given past error in the national generic ballot polls — identifying vulnerable seats that could be won by either Democrats or Republicans.

Race Ratings

Each seat is given a vulnerability rating based on the following scale for either party:

  • Tossup: win margin <5%
  • Lean Dem./Rep.: win margin >5% and <15%
  • Likely Dem./Rep.: win margin >15% and <25%
  • Safe Dem./Rep.: win margin >25%

Ratings also take into account qualitative factors like candidate characteristics, contest dynamics, fundraising, etc. And, as a general rule, no open seat forecast to change parties will ever be rated “Safe.”

These ratings are available on the model’s companion post at DDHQ


Possible Outcomes


Of course, there is error in our forecasts — measurable error. We can account for that error by simulating the election thousands of times, asking the computer each time to pick random error for national polling that is based on error from past predictions. Then for each “election’s” national error we also generate an error for each congressional district, basing each of those 435 individual errors on what the error is in districts that have performed the same in the past. (So, for example, if a simulated error adds 4% for the Democratic candidate in a district that voted for Romney and Trump by 5%, the error would around 4% for other districts that voted similarly. This is called correlated random error.)

Here’s the distribution of total number of Democratic House seats after engaging in that exercise:

We can take all of those simulations of Democratic seat shares and further ask “what is the chance that Democrats win the election, given the chance that Democrats or Republicans beat expectations?”

Democrats have a 45.1 percent chance of winning a House majority on November 6th, 2018. You can imagine that the rectangle below is a dart board, and if you randomly threw a dart anywhere at the rectangle whichever square you land on corresponds to the party that wins the House majority.



FAQ


Note: This page will continually be updated, both with new data and new features, from now until Election Day! Come back regularly for a different look at the 2018 midterm race. If you notice something missing let me know.


Data


Polls

Seat forecasts

Simulated seat shares

Polls, vote projections, seat shares and win probabilities over time


Forecasts For Every House Seat