This prediction has been replaced/updated with this one.
I have added new models to my previous prediction of a Republican gain of 61 seats in the House.
First, one must predict the vote totals for each party. Currently, RCP’s average of the “Generic Congressional Vote” shows Republicans winning 49.3% to 41.6%. However, you clearly see two outliers, one to the upside (Gallup LV Lower Turnout) and one to the downside (Newsweek). Excluding those two gives you a pretty tight pack varying from +7 to +11, a small 4 point range versus the huge 20 point range if you include the two extreme polls. Based on these five closely-packed polls, Republicans lead Democrats 49.8% to 40.6%. Eliminating the undecideds (if they have not decided by now, they are unlikely to vote) gives a two-party vote total of 55.1% for the Republicans and 44.9% for the Democrats.
I now have three models to convert vote totals to House seats.
40-year model: Regression of House seats vs. vote total for every election since 1968.
8-year model: Regression of House seats vs. vote total for every election since 2002. Because of the increase in partisanship and computerized gerrymandering, there are now many more safe seats.
1994 & 2006 model: In these two mid-term elections, control of the House switched sides against an unpopular President. The same will likely occur this year.
The models produce the following results:
40-year model: Republicans win 268 House seats, gain of 90 seats.
8-year model: Republicans win 247 House seats, gain of 69 seats.
1994 & 2006 model: Republicans win 253 House seats, gain of 75 seats.
Taking a simple average of the three, I now predict the Republicans will win 256 House seats, a gain of 78 seats.
* Again, I will update these numbers as new polls come in. But if you look at the polls on RCP over the last month, Republicans have been consistently in the lead by 8 or 9 points. Barring some late breaking change in this election, I don’t expect these number to change much. But who know how accurate the polling is this year? We won’t know for certain until November 2.
Michael E. Newton 
RCP added a new poll to its list. Politico/GWU/Battleground’s Generic Congressional Poll has Republicans up by 5 (47-42). This brings down the average spread in my model (excluding the highest and lowest polls) from 9.2% to 8.5%.
As a result, my prediction of 78 House seats to be gained by Republicans has now dropped to 75 seats. The new range is 67-86 seats (down from 69-90).
Gallup just came out with its latest poll. Gallup (LV Higher Turnout) went from R+11 to R+9. Gallup (LV Lower Turnout), which gets thrown out as the highest poll, went from R+17 to R+14.
At the same time, Rasmussen’s poll stayed stable at R+9.
As a result, my prediction drops again; this time from 75 seats to 73 seats with a range of 66 to 84.
With three new polls out today, my prediction has dropped from a GOP gain of 78 seats to 73 seats. Clearly, as I wrote above, “Republicans have been consistently in the lead by 8 or 9 points. Barring some late breaking change in this election, I don’t expect these number to change much.”
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Another new poll is out. CBS News/NY Times puts Republicans ahead in the Generic Congressional Vote 49% to 43%. That 6% margin is slightly below the 6.9% margin RCP Average and my 8.2% margin (49.3%-41.2%).
As a result, Republicans now have a 7.9% margin (49.3%-41.4%) in my models. Therefore, I am revising down my prediction for GOP seats by 1 to 250 seats, a 72 seat gain.
Another poll out and like the CBS News/NY Times out earlier today, the McClatchy/Marist shows the very same 49% to 43% margin. The RCP Average dropped from 6.9% to 6.5%, mostly because RCP dropped the oldest poll, a Fox News poll from 10/11 – 10/13.
I added the McClatchy/Marist poll and dropped the Fox News poll as well. My models now show the Republicans gaining 63, 68, or 79 seats. Therefore, I am revising my prediction for GOP seats by 2 to 248 seats, a 70 seat gain.
When I first used these models on Sunday, I predicted a 78-seat pickup for Republicans. Now it is down to 70. Is this the beginning of a trend? Are the Democrats really making headway in the last week?
Another issue is early voting. Many people have already voted and this change in the polls will not affect how they vote. How exactly do the polls account for early voting? If there is a sizable change in opinion, and not just statistical noise, are the current polls reflecting current opinion or current opinion AND how people already voter. Once somebody votes, they can’t change their vote but they can change what they tell pollsters. Furthermore, are early voters more or less likely to answer telephone polls, thus skewing the results toward the end of the election? If anybody knows, do tell.
Is the Republican slide continuing? Bloomberg came out with a Generic Congressional poll showing the Republicans up by just 3 points, much lower than RCP’s previous 6.5 point margin. However, the last time Bloomberg did a poll (10/7 – 10/10) they had the Democrats up by 3. Clearly, Bloomberg tends toward one side yet even they have seen a Republican trend over the last two weeks. But since RCP is including this poll, I will too.
Additionally, Zogby came out with a poll yesterday showing Republicans ahead by eight points. But for some reason (anybody know why?) RCP doesn’t include Zogby.
Using the new RCP numbers but dropping the highest and lower polls, the Republicans are now ahead 49.1% to 42.3%, a 6.9% margin (RCP has a 6.0% margin). Using this data, my three models predict the GOP will gain 61, 66, or 77 seats. So my current projection is for a 68-seat gain for the GOP.
On Sunday, I had forecast a 78 seat gain. Clearly Democrats have recovered somewhat over the last week. However, most of the decline is due to new polls, not changes within the polls. For example, Rasmussen remains stable at a 9 point margin for Republicans but Gallup now has Republicans up by 9 versus a margin of 11 points last week. Certainly, Republicans have seen their margin narrow, but not as much as the RCP average shows. The question remains whether Sunday’s margin was too high or today’s is too low. We won’t know for sure until Tuesday or Wednesday.
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