Princeton Election Consortium

A first draft of electoral history. Since 2004

Presidential prediction 2012 (Election Eve)

November 6th, 2012, 1:47am by Sam Wang


If state polls perform as well as they did in 2004 and 2008, most aggregators should get within +/-15 electoral votes and 48/51 races correct. The question is how to squeeze a bit more out of the data.

The topline listed just below the title of this website is not our prediction, but the automatically-generated snapshot. It will fluctuate as the last few polls trickle in. The last 3 updates are at 8:00am, 10:00am, and noon. Then we freeze it.

I make two electoral predictions.

ELECTORAL PREDICTION (mode): Barack Obama 332 EV, Mitt Romney 206 EV. The mode is the single most frequent value on the histogram. It corresponds to the map below, and has a chance of being exactly correct.

ELECTORAL PREDICTION (median): Obama 309 EV, Romney 229 EV, Popular Vote Meta-Margin Obama +2.34%. This is  the automatically-generated snapshot for November 5th 8:00pm. This prediction is almost guaranteed to be off, since 309 EV is not a common combination. (Note: I’ll edit this with the last few updates.)

ALL-STATE PREDICTION (binary outcomes):

Most outcomes arose clearly from the median of the last week of polling. The exception was Florida, for which I used polls with at least half of their respondents on Nov. 1 or after. This gave a median margin of Obama +0.5 +/- 0.8% (n=10), for a win probability of 72%. I will be unsurprised for it to go the other way (outcome Obama 303 EV, Romney 235 EV). In Florida, a recount is triggered by a margin of 0.5% or less (recount rules, Brennan Center for Justice). There is about a 50-50 chance that we will see that happen.

The next-closest states are Colorado, Virginia, and North Carolina, with margins of less than 2.0%. Excluding these three states and Florida still leaves Obama 281 EV, Romney 191 EV.

In addition to all-or-none outcomes, later today I will provide final polling medians in graphical form in the Geek’s Guide. I hope it will be useful as you follow the returns.

POPULAR VOTE. The average Meta-Margin for the last three days was Obama +2.7%. The median of national polls is Obama +1.0 +/- 0.5% (n=13 polls). The approach I described before for combining these measures gives

  • Final predicted popular-vote margin: Obama +2.2 +/- 1.0%.
  • Two-candidate vote share: Obama 51.1%, Romney 48.9%.
  • Allowing 1% for minor-party candidates: Obama 50.6%, Romney 48.4%.

Finally, here is a look at the histogram as it stands tonight. The EV histogram has resolved to just a few peaks because so few states are in play – the four states I mentioned before, plus maybe Iowa. I’ll update this with a cleaner version with longer-term-integrated probabilities in the morning.

 

I should point out that A note: Election Eve prediction is not the most impressive of feats. What we did in August (here, and here) was the interesting part. Those were true predictions, and were centered around Obama 315 EV, Romney 223 EV.

Put your predictions in comments.

Tags: 2012 Election · President

294 Comments so far ↓

  • buffalo rich

    Thanks Dr. Wang and the regular posters for making this site a beacon of sanity and accurate information in a time when I realized even the liberal media was willing to forgo accurate reporting in order to slake its thirst for corporate profit.

  • Stephanie

    I am making calls in Portland OR right now! We are out in force all over! Oregon blue state taking no chances!

  • Jwill

    I rolling with Doc. However, I have feeling that the final count will be 303 for Obama.

    If it’s 332, I’m taking a shot!

  • TAW

    More on Intrade:

    Current — Obama $6.95. I think it is effectively too late to wire money to buy Obama.

    However Bovada — http://sports.bovada.lv/sports-betting/political-props.jsp has Obama @ 1-4. Romney @ 3-1.

    There is theoretically room to arbitrage.

    In 2004, I lost $500 betting on Kerry based on the exit polls and wishful thinking. This was the old Bodog online casino.

    I am more comfortable betting with pros than the Intrade people.

    I don’t bet on eating bugs, but Horses and Elections Sure.

  • SouthernFried

    I voted today in my little precinct in a little Southern state that Romney will win by more than 25 points. Three hours after polls opened, there wasn’t much of a line, but then there never is.

    If the polls are correct, I expect the outcome to be:
    O 303 (winning all swing states except NC & FL)
    R 235

    However, let it be known here and now that I am a major-league pessimist, and I’m expecting the state polls are in fact NOT correct, and they have underestimated Romney’s support to a significant degree (over 3pts), and that the pundits and crazies will actually be right for once. Therefore, my “Pessimist’s Projection” is:

    Romney 285
    Obama 253
    PV: R=50.5, O=48.5, J=1

    Romney wins all swing states except NV, which he loses by less than half a point. PA goes for the president in the end, but by less than a quarter of a point because Sandy. OH isn’t “stolen” like FL was in 2000, but the GOP does successfully prevent enough minorities from voting to take it.

    I would not be shocked at all if Romney snags PA & NV too, giving him 311. There’s even an outside chance that R/R wins their “home states” of WI & MI if the polls are as off as I’m expecting, so make the upper EV total 337R to O201.

    From what I have gleaned from folks around the net, the numbers coming out of the swing states are very very bad for the president.

    And no, I’m not a GOP troll. I’m a pessimist who always assumes worst possible outcome. It’s not a good way to live; I don’t recommend it.

  • don in fl

    ohio is scary.fl.if obama wins this state it will have to be hispanics in the I4 corridor and south fl.not going to win in the north or panhandle area.got my vote though.

  • Brian

    Marcus // Nov 6, 2012 at 9:31 am

    Romney 275
    Obama 263

    Popular vote 50-48 R.

    And then I wept myself to sleep.

    ____________________________-

    I wonder if this will make it past the good professor’s censor.

    Crack is a hell of a drug.

  • Dan Ollendorf

    T.S. Eliot — great poet. Just wish his need for exploration extended to his own character, which featured an obsessive need to be a racist and anti-Semite.

    • Sam Wang

      One can find very unattractive things in another person’s character. Yet such people often accomplish great things. Aside from that, the lines were so appropriate today.

  • Alex

    Good job Dr Wang.
    Your observations were on the money.

  • A

    Um, NAILED IT. And thank God. 126 EV margin, holy moly…

    The 2004 comparisons understate what happened here. Bush won by one state. Obama could have given Florida, Ohio, and Virginia and still triumphed. We’ll see who the candidates are next time, and what happens in the next four years, but I wouldn’t want to be (for any number of reasons) in the GOP.

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