What will we know on Tuesday at 7pm?

On the evening of November 8, 1988, I was working with my colleague Gary King in his Harvard office. Gary somehow had gotten his hands on a pair of tickets to Michael Dukakis’s victory party in Boston, and we were trying to decide whether to go. Dukakis was expected to lose, but . . . who could say, right? We had the TV on, and the first state to report, at 7pm, was Kentucky, which Bush had won by over 10 points. Gary informed me that the election was over: Kentucky, at the time, was near the political center of America, and there was no way that Dukakis would do much better nationally than he did in Kentucky. So we saved ourselves a subway ride and kept on working.

What about this year’s election night? Can you play along at home with the election and decide at 7pm what is happening? We will perform some calculations using vote margin (as we learned of Kentucky in 1988) and some using only the tally of states won or lost.

I did all the calculations using 10,000 simulations from Nate Silver’s latest election forecast.

At 7pm, we’ll hear from Virginia, Indiana, Georgia, South Carolina, and Kentucky (and also Vermont, which I’ll ignore because of its atypicality). Based on current poll aggregates, we expect the average vote margin in these 5 states to be 5.7 percentage points in favor of McCain.

The top row shows the uncertainty distributions for the popular and electoral vote (Obama wins are shaded in each case). The bottom row shows the corresponding distributions, conditional on the above five states going exactly as expected, with an average McCain victory margin of 5.7 points.

homegame1.png

So, if things go as expected at 7pm, it’s all over. But what if things don’t go as expected? The simulations show that the average margin in the five 7pm-closing states could be anywhere from 12 points in favor of McCain to 1 point in favor of Obama. The next graph shows Obama’s expected popular vote margin, electoral vote, and probability of winning under a range of 7pm outcomes.

homegame2.png

Finally, we did some calculations based on the scenario in which we don’t know the vote margins but we do know who wins each state. Here’s the story of the key 7pm-closing states:

homegame3.png

And then, if McCain wins Virginia, it goes on from there. . . .

See here for the full paper.

5 thoughts on “What will we know on Tuesday at 7pm?

  1. This is so cool!

    For those of us in Europe (where 7pm EST is midnight) we can easily check whether or not to stay up later… Or if it safe to go sleep knowing Obama has won.

    thanks!

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  4. If Obama takes MO , you will have the perfect prediction 375-163 .
    ( I assume 1 was lost due to rounding).
    Congratulations!

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