The formula for contested House races is substantially unlike the previous formula. There are several differences between this
formula and the one used for Senate and gubernatorial races.
First, published polls for district races are much more difficult to find than for other races, so I need another
metric which would be reliable and consistent throughout the election season. The aggregate race ratings of three well-known political pundits is that
metric. The predictions of Charlie Cook, Larry Sabato and Stuart Rothenberg will be used. Since their
predictions are qualitative (i.e. leans, toss-up, safe, etc), I will assign a margin of victory to them as follows:
Second, when polling data can be obtained, their weight will be based on whether one poll or multiple polls are available. If one poll is
available, it will get a 25% chunk of the projection. If two polls have been published, the average will be taken, and
that result will be 50% of the projection. Currency stipulations posted in the Senate and gubernatorial formula explanation will apply here
as well (there will be no exception if only one poll has been taken in the last 14 days).
Third, partisan polls will be used with a caveat. The results will be adjusted by subtracting 2 points from the party of the pollster and
adding them to the other party. For example, if a Republican polling firm publishes a poll with the GOP candidate winning 54% to 40%, the poll will be
entered into the calculations as 52% to 42%.
Fourth, an adjustment will be applied to the projection after the pundit rating and polls are included in the calculations. This adjustment
will be based on an average of all published generic congressional polls released in the previous week which test for likely voters. Conventional wisdom holds that a
slight Democratic lead (2 points) in the general poll average translates to a status-quo electoral result. However, after the red wave election of 2010 which left the
balance of power in the House substantially out of balance, that conventional wisdom may not apply.
In that election, Republicans enjoyed a 7-point advantage over Democrats in all votes cast for House candidates across the nation. That represents a 9-point shift
away from "a level playing field." To compensate for this shift, I instituted a new composite generic offset in 2012. That year the offset split the difference
between the normal DEM +2 value and the actual GOP +7 mark from four years ago. Therefore the 2012 baseline was GOP +2.5 points.
This year, the GOP majority is slightly reduced after a good election for Democrats in 2012. To compensate, I am adjusting the 2014 baseline to GOP +2.0. At this mark, the adjustment will be zero.
Each point in either direction from the GOP +2.0 baseline will increment the adjustment by one-quarter point. In other words,
a generic average of DEM +2.0 would produce an adjustment of 1.0 point for the Democratic candidate in each tracked House race. Likewise, a GOP +3.6 average
would result in a 0.4-point adjustment for the Republican.
For races with no published polls:
(Pundit Avg. * 100%) +/- generic poll adjustment
NOTE: Because I refuse to post a "toss-up" rating on any race, I will decide one way or the other in the event that
pundit predictions and the adjustment result in a tie. The margin for such races will be +0.5% for my best guess.
For races with one published polls:
((Pundit Avg. * 0.75) + (Poll * 0.25)) +/- generic poll adjustment
For races with two published polls:
((Pundit Avg. * 0.50) + (Poll * 0.50)) +/- generic poll adjustment
Here is an example of the calculations using the formula:
Pundit Predictions: Raw value = 7.0 for the Democratic incumbent
Stuart Rothenberg: Democrat by 8% (likely DEM)
Charlie Cook: Democrat by 4% (lean DEM)
Larry Sabato: Democrat by 4% (lean DEM)
Polls: Raw value = -2.0
XYZ Polling Company (R): Republican (R) 44%, Democrat (D) 38%
Generic Adjustment: -0.5
Congressional generic poll average: GOP 43%, DEM 43%
Projected Result: |(-5.3 * 0.75) + (-2.0 * 0.25) + (-0.5)| = 5.0%
Democrat projected to defeat Republican by 5.0%