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Outcome: Biden 306 EV (D+1.2% from toss-up), Senate 50 D (D+1.0%)
Nov 3 polls: Biden 342 EV (D+5.3%), Senate 50-55 D (D+3.9%), House control D+4.6%
Moneyball states: President AZ NE-2 NV, Senate MT ME AK, Legislatures KS TX NC

Predictions 10/6: House of (un)Representatives

October 6th, 2012, 12:01pm by Sam Wang

I am in complete suspense over who will control the House. As far as I can tell, things are about as much on a knife edge as one could imagine – despite a Democratic lead in polls. Why?

Unlike the Presidential and Senate races, the outcome of House control depends critically on events in the coming weeks. Voter enthusiasm will almost certainly be the determining factor. I agree (!) with Bill Kristol that the Obama-Romney margin will be strongly predictive; 3% or greater will suggest a likely Democratic takeover of the House.

I have evaluated incumbency and redistricting advantages quantitatively. I now believe that these two phenomena contribute approximately equally to an overall advantage of R+2.5+/-1.0%. In other words, Democrats need to win the popular vote by 2.5+/-1.0% in order to achieve near-parity in House seats. I was wrong about thinking there was little tilt in the playing field. It’s substantial.

Today’s prediction uses the generic Congressional ballot median since the conventions, currently D+2.5+/-1.0% (18 polls). Between now and the election, it is likely to move a few points in one direction or the other. Undecideds are at 10.5+/-0.8%. This month, a very large shoe will drop.

It is critical to pay attention to the uncertainty here: +/-11 seats.

House prediction, October 6th:
Two-party popular vote share: D 51.3 +/- 1.5 %, R 48.7 +/- 1.5%.
Seats*: D 217.5 +/- 11 seats, R 217.5 +/- 11 seats.
Uncertainties are 1-sigma (68% of outcomes).

Technical notes on this calculation are here. I would rather you not focus on the party-control probability, which is basically 50-50.

In the coming weeks, a better prediction will be possible two ways: (1) the freshest available generic polls, and (2) using district-specific polls, as collected by RealClearPolitics or


A few days ago I met Bill Foster, physicist and Democratic candidate for Congress. He said that the DCCC was implacable. If a candidate is on the edge but has a fighting chance, he/she gets DCCC financial support. Too far ahead or too far behind? No money. Exactly what I would recommend. Here they are, along with knife-edge Senate races. And here is Crossroads GPS, which does the same for Republicans.

*The post originally said D217, R218. However, the actual median prediction is 217.5 each. Therefore I have changed it to reflect that. Normally I don’t like to give half-seat predictions. In this case, it has the advantage of conveying the situation to people who do not notice the error bar, which is +/-11 seats – not horrible, but the race is so close.

Tags: 2012 Election · House

12 Comments so far ↓

  • Steve16748

    I know what would super energize me to drop everything and work full time for the Democratic Party through Nov. 6. Harry Reid and the rest of the Democratic leadership promised to vote the filibuster into oblivion on resumption of the new senate. I’m getting old and I would like to live in a modern western democracy before I die.

    • Sam Wang

      You mean like what he said here?

    • MarkS

      This is why I am directing all my contributions to the Democratic Senate candidates recommended by Sam, rather than to the DCCC or Obama.

    • pechmerle

      This is from the same source as Sam’s citation about Harry Reid’s promise:

      “If the Democrats keep control of the Senate on Nov. 6, it is unclear whether they will have the 51 votes they would need to implement Reid’s proposal. Some veteran Democrats, as well as those from Republican-leaning states, could resist the weakening of the filibuster.”

      This is the view that I have noted previously on this site. When push comes to shove, I just don’t think the votes will be there. There will be enough Senators who don’t want to give up leverage by changing this (anti-democratic) rule. The public is not strongly involved with this issue, which is too technical for most people. In the recent past, both parties have squawked very loudly when the other party in the majority has threatened to change the rule. Not for nothing has changing the rule come to be called “the nuclear option.”

      Another avenue is being attempted: a lawsuit in federal district court in D.C. brought by Common Cause and others contending that the Senate’s 60 vote filibuster rule is unconstitutional. The basic idea is that the Constitution provides that a bill becomes law by being passed by a majority in each house and signed by the president. The Senate rule, it is argued, creates a super-majority requirement that is in contradiction with the Constitution and therefore invalid. The lawsuit is here:
      For those of you interested in this constitutional issue and the history of the filibuster rule, I recommend the first nine pages. They read fairly well for a non-technical audience. After that it gets into the constitutional case law, and would be difficult to follow if you aren’t familiar with the cases.

      I agree with the plaintiffs in principle, but I think they are quite unlikely to succeed with this Supreme Court. (And would be unlikely to succeed with the composition of most Supreme Courts that we have had.)

      Bottom line: I predict that — come January — the filibuster rule will not be changed. (Something else might happen, such as a renewed informal bargain between Reid and McConnell on how matters such as appointments will be handled.)

  • Ebenezer Scrooge

    I do think that there is a third significant factor influencing House races that doesn’t show up in the raw polls: Obama GOTV. Most of the marginal voters dragged to the polls by GOTV will vote the party line. (Most voters vote the party line, but I would suppose that ticket-splitting might be more common among voters who would go to the polls anyway.)
    A purple state at the Presidential level will benefit from Obama GOTV; a bright red or blue state won’t. That could make a 1% difference.
    Expect VA, OH, FL, NV, CO to show blue anomalies downticket. Don’t expect this from MA, ND, IN, MT, CT, AZ–all states where the presidential race is foreordained. This strengthens Sam’s argument for contributing to Warren, Heitkamp, Tester, Donnelly, and Murphy. You might want to throw Carmona into the mix.
    Come to think of it, Sam isn’t recommending any purple Democrats: Kaine, Nelson (who is far ahead in any case), Berkley, Baldwin.

  • Amitabh Lath

    Kudos on getting the House prediction out. I know how much work it must be, so much more than the presidential race. I am still going through your linear regressions for polling margin vs seats gained.

    Your gerrymandering correction technique looks reasonable. I am shocked at how huge the value is.

    But this is important. The House is our democracy in the trenches. Thank you again for doing it. I have already donated to Bill Foster. Let us know if there are other worthy candidates.

  • Silvio Levy

    The math in The Very Hungry Gerrymander (October 4th, 2012) seems to me impeccable, but I wonder if the historical model is a good predictor in this case. The Republican Party of the 21st century seems much more aggressive than Democrats have been in the past in manipulating the levers of power for partisan advantage. Just consider how the Medicare bill was passed in December 2003, or how the “painless” filibuster has been used routinely in the last four years, compared with the parsimony with which it was used by Democrats under G. W. Bush.

    My impression is that, while there was some gerrymandering by both parties in the comparison period 1946-1990, Republicans have been much more aggressive — and effective — at the game in the last two cycles.

    Anyway, I hope you’re right that the playing field is “only” tilted by 2.5% +/- 1% in favor of Republicans. This at least gives Pelosi a fighting chance.

  • Olav Grinde

    It’s very interesting to read your in-depth revisiting of the House predictions! And as you point out, that voter enthusiasm and turn-out will have a huge effect on down-ticket races.

    I could not help but notice the latest PPP poll of Wisconsin, which shows Obama +2% over Romney. The last PPP poll in this state (18–19 Sept) showed Obama at +7%.

    Now, I realize that this is meagre data and no hasty conclusions should be drawn — but that’s a 5% drop in comparable polls!

    I cannot but wonder whether Obama’s mediocre debate performance might not — first and foremost — have a profound negative effect on Democratic enthusiasm and turnout, with catastrophic results on down-ticket races, both in the House and at the state level.

    • Anbruch

      PPP said that the shift in WI was almost entirely due to increased enthusiasm among GOP voters, rather than increased support from independents. PPP also said that Friday’s numbers were much better for Romney than Thursday’s numbers, and this was true of their other polls as well. I’m not sure what to make of that apparent Friday surge, if it wasn’t simply noise, except that it was accompanied by the weird accusation about BLS manipulating the unemployment statistic.

    • xian

      @Anbruch, I would suppose it was the full consensus sinking in that Romney won the debate, and probably a lot of confirmation bias experiences around the “lazy” Obama who is bad without a teleprompter, etc. (so easy to forget him debating the entire Republican caucus off-the-cuff just about two years ago).

  • Sam Wang

    Technical comments are welcome on the methods post linked from this post.

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