Andrew Sullivan has collected some commentary that argues against my suggestion that the House could potentially flip in 2014. There were some good points made. However, it should be noted that some of these analysts’ comments have been OBE (Overtaken By Events) – the shutdown. The incredible numbers in yesterday’s NBC/WSJ poll pretty much demonstrate that point: approval of the Republican party is at an all-time low…and 60% of voters would vote out every single member of Congress at once including their own if given the chance.
All of the arguments on this subject can and should be quantified. It’s just like last year’s Presidential race: is any of this punditry data-based? Today I start to outline a true prediction. I give a “toy model,” i.e. step 1 toward something more realistic. The toy model relies on a prediction of popular vote only. At the end, I start to add a little bit of complication. I invite you to add more complication in comments.
Provisionally, it looks like the following: In a little over a week, the shutdown has increased the probability of a Democratic House takeover in 2014 from 13% to as high as 50%.
The first number (13%) is is exactly as expected if House trends were following expectations from analysts’ conventional wisdom and political science research. But the shutdown, combined with the fluidity of gerrymandered districts, has added a highly unexpected twist. The 50% figure could swing back toward the Republicans, or it could go further toward the Democrats. For certain, it gives a measure of an unusually fast change in the national mood. Let’s dive in.
Predicting the nationwide vote. Kevin Drum suggests that Congressional candidate preference polls a year out are not all that predictive. But they might have just enough value to be useful. Quantifying that value is a key step in turning my presentation yesterday (which was a snapshot) into a true prediction.
To project current Congressional opinion forward in time, we have to quantify Delta, the difference between opinion in October of the previous year and the actual national election vote. Using generic Congressional ballot data from RealClearPolitics, I get the following:
|Year||1 year before||Outcome||Delta|
|2002*||D+0.0%||R+4.6%||Toward R 4.6%|
|2004*||D+1.5%||R+2.6%||Toward R 4.1%|
|2006||D+8.0%||D+7.9%||Toward R 0.1%|
|2008||D+12.0%||D+10.7%||Toward R 1.3%|
|2010||D+1.0%||R+9.4%||Toward R 10.4%|
|2012||D+1.0%||D+1.3%||Toward D 0.3%|
|Average||D+3.9%||D+0.5%||Toward R 3.4 +/- 4.0%|
The correlation between polls now and eventual outcome is r=+0.89, which is pretty good. Basically, polls now are fairly predictive of Election Day, but Democrats are likely to lose ground by then**. The average movement is Delta=3.4% toward Republicans, with a standard deviation of 4.0%. To account for further uncertainty, I will bump that standard deviation up to 5.0% for prediction purposes.
Let’s make a prediction of the national popular vote, based on pre-shutdown conditions. The last data points before the shutdown gave D+5.0% (Quinnipiac, Rasmussen, PPP, Sept. 23-29). Adding in the expected drift, that translates to an average predicted popular vote in November 2014 of 5.0-3.4=D+1.6%. This is similar to the 2012 election, when Democrats won 1.3% more votes (but not more seats).
Now let’s make a second prediction, this time based on post-shutdown data. One piece of information is my previous analysis of the MoveOn data indicating a swing of 8 points away from Republicans, and 14 points in gerrymandered districts. That number comes from a surveys for specific Republican members of Congress, paired with a generic Democratic challenger. In short, the MoveOn data is equivalent to current conditions of D+9% nationally.
Harry Enten and Nate Cohn speculate that the MoveOn/PPP polls might not be accurate, either because (1) asking “Congressman vs. Generic” gives an unfair advantage to Generic, perhaps because (2) Democrats might run a bunch of lame candidates. But the generic Congressional preference question has the same issues and has a rather good track record. Recent generic-Congressional surveys (D+4%, D+5%, D+8%) are not so far from the MoveOn prediction for non-gerrymandered districts. However, I agree with Enten that it would have been good to have data for some Democratic districts.
Combining the MoveOn data for non-gerrymandered districts with the other post-shutdown polls gives a median margin of D+6.5%. Projected forward to November, that’s a prediction of D+3.1+/-5.0%, which means that Democrats have a 73% probability of winning the national popular vote in 2014.
Converting votes to seats. If shifts in opinion occur nationwide by the same amount in every district, the probability of a Democratic takeover is the probability that their popular margin will exceed D+7%, the threshold number in the 2012 election. Then the probability of Republican retention of the House would be 78% post-shutdown, or odds of 4-1 in their favor. That is not so far from most analysts’ views. (To put this in perspective, applying this method in October 2009 would have predicted the 2010 GOP takeover with a probability of about 70%.)
However, the shutdown has upended things, and the shift is not equal across districts, as indicated by the MoveOn data. To repeat yesterday’s point, gerrymandered districts have swung by an average of
14 16 points against Republican incumbents. (Note, 10:47am: 12 new PPP polls reinforce the picture. Gerrymandered R’s have slipped an average of 15.6%, compared with 8.6% for non-gerrymandered R’s. It’s highly significant, p=0.01 [spreadsheet].)
The gerrymandered districts are shown in white.
If gerrymandered districts swing harder, that puts dozens more seats into play. If the finding holds up (needs more data!), that brings the probability of Republican retention down to around 50%.
Whether or not this holds up precisely, let’s look at the big picture: The usual midterm outcome would lead to a gain of seats and votes for Republicans. But the change in national mood has changed the narrative. The GOP is likely to lose the popular vote, and even lose seats. I believe that Republicans are still slightly favored to retain control…but that depends on what they do in the coming weeks and months.
From an analytical standpoint, this is somewhat mind-blowing. Think about it: the shutdown has turned a likely Republican lock in 2014 into a situation where their political survival hangs in the balance. That is quite an accomplishment in one week.
*Data are from October in the year before the election, except for 2002-2004, which are data for January in the year of the election.
**Bafumi, Erikson, and Wlezien have a different interpretation based on data going back to 1946: over that period, that midterm opinion during the year tends to move against the incumbent president. For Democratic presidents, the shift from January to November is about 6.7 +/- 3.4%. Applying that rule would predict a near tie: R+0.2+/-3.4%. However, note that the rule has been seriously violated twice in the table above. Politics is in a disrupted period, so I’ll take my value above for now.
***It is also consistent with the finding (Bafumi et al., op. cit.) that a party’s midterm popular vote tends to lag the previous Presidential vote by 3.3+/-2.6%. This predicts D+0.7+/-2.6% in 2014. However, there’s a long tail on that distribution; Republicans gained 3 points in 2002, totally contrary to Bafumi-driven expectations.
In other words, based on Bafumi et al. the pre-shutdown generic Congressional vote and the 2012 election result lead to the same prediction, and match analyst conventional wisdom. But Enten, Cohn, Sullivan, and others, think of it like this: Republicans losing the House would only come to pass if something strange and big happened to alter the national mood. What do you think is happening right now?