Posted by: Dr. Grover B. Proctor, Jr. | 17 October 2014

Silver’s Crystal Ball, Part 2


In part 1 of this pre-election series, I re-introduced you to Nate Silver. He’s the young probability/statistics guru who, unlike all of his peers in the business, correctly predicted the results of the 2008 Presidential race in 49 of 50 states, and the results of the 2012 Presidential race in all 50 states. I remain quite curious to see how well he will do in these off-year elections.

This is the first of the four Friday updates to my initial article, leading up to Election Day, to see how Silver’s Senate election predictions evolve, if they do — and, afterwards, to see how much he got right.

Last week, Silver’s projection was a 58% likelihood that Republicans will win control of the Senate this election.

As seen in the graph, this week his projection has widened the chance for the GOP. He now sees a 62.2% likelihood that Republicans will control the Senate, and only a 37.8% chance the Democrats will keep it.

Control of Senate Probability Predictions

Analysis and Graph by Nate Silver (17 Oct 2014)

Kay Hagan and Thom Tillis

Senator Kay Hagan and Speaker Thom Tillis

North Carolina Senate Projection Percentages
In the North Carolina race, Silver is still predicting a 47.5-44.7 percentage point Kay Hagan (D) victory over Thom Tillis (R). However, he has lessened ever so slightly the probability of that win from 79% to 76%.

(Please note that when I use the shorthand “Silver predicts victory…,” I am saying that, in that race, his percentage probability of victory for that candidate currently sits at greater than 50%.)

Of the 36 Senate races being decided (including special elections in Hawaii, Oklahoma, and South Carolina), Silver’s predictions are unchanged since last week, showing Republican wins in 22 states and Democratic wins in 14. These include 8 Democrat-to-Republican pick-ups in Alaska, Arkansas, Colorado, Iowa, Louisiana, Montana, South Dakota, and West Virginia. The only Republican seat he is predicting they will lose is in Kansas.

Maroon 6 States Predictions
The Maroon 6: Silver has identified six states that he calls the “Maroon 6,” with Senate races to watch: Alaska, Arkansas, Georgia, Iowa, Kentucky, and Louisiana. His calculations tell him that if Republicans win all 6, they have a 99% chance to take the Senate. If they win 5, their chance slips slightly to 84%. With anything less than 5 wins, however, Republicans’ chances to control the Senate drop precipitously, to levels that strongly predict Democrats’ keeping the Senate. Right now, on his state-by-state projections, Silver’s predictions of Republican victories in all 6 of the Maroon states remains unchanged, though he says the race has tightened slightly in Georgia.

Other Predictions:

  • The New York Times‘ online TheUpshot page currently predicts: “According to our statistical election-forecasting machine, the Republicans have a moderate edge, with about a 70% chance of gaining a majority.” They predict an 81% likelihood that Kay Hagan (D) will defeat Thom Tillis (R), and that the margin will be +2.9 percentage points.
  • The Washington Post’s Election Lab states: “Republicans are favored to control the Senate. 96% chance as of today.” They give Kay Hagan (D) a 95% chance of keeping her seat.
  • When forced to make best current predictions for all Senate races (including those they now call “toss-ups,” Real Clear Politics predicts an 8-seat net pickup by the Republicans, giving them a 53-47 majority. They list the NC Senate race a “toss-up,” showing Kay Hagan’s (D) current margin over Thom Tillis (R) a mere +1.4 percentage points.
  • Rasmussen Results currently labels the NC Senate race a “toss-up.” In their most recent poll (taken Oct. 6-7), Hagan (D) polls at 48% and Tillis (R) polls at 46%. The margin of error in that poll of likely voters was +/-3 points, placing these results within that range.

That’s all until next Friday.

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