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The November 6th US Midterms – where we are and what might happen

October 28th, 2018

Viewcode looks at the detailed data

The main elections on November 6th  are for 435 seats in the House of Representatives, 35 of the 100 seats in the Senate, 36 out of 50 state/district Governors, and 3 out of 5 territory Governors. This is an attempt to summarise the predictors. The following figures were taken between 11pm BST October 27th and 3:30am BST (2:30am GMT) October 28th 2018.

Nationwide generic ballot polls

The United States is a large country with an unevenly distributed population and certain quirks on mobile phone ownership and voter registration which makes building a representative sample frame (the list from which a sample is taken) somewhat of a challenge.

Nevertheless “generic ballot” polls are conducted. A “generic ballot” poll asks the person which party they would prefer to control Congress or would vote for in their district. The website FiveThirtyEight has a page summarizing those polls and the spreadsheet is here. The last six polls so listed are here:

State level polls

Due to time constraints this will not be considered

Number-Crunchers

Just like the United Kingdom, the United States has a rich ecology of analysts and academics who produce their own predictions of the outcomes. Their predictions are complicated by the concept of a “toss-up” or “too close to call” (TCTC): elements which they decline to predict, and by the use of qualifiers such as “Tilt”, “Lean”, “Likely”, etc. A summary of the predictions can be found on the Wikipedia election pages for the Senate  and House of Representatives.

Senate

Two senators (Angus King and Bernie Sanders)  are Independent but “caucus” (vote) with the Democrats. They are considered to be safe in their seats and are included with the Democrats in the table below. 35 seats are contested (24+2 Democrats, 9 Republicans). CNN has a named predictor (Harry Enten) and other predictions.

House of Representatives

All 435 seats are up for election. No independents. ). CNN has a named predictor (Harry Enten) and other predictions. The Daily Kos site is not clear enough for me to easily extract the data. 538 gives three options (lite, classic, deluxe) and two modes (one by probability, one by district). I have chosen the classic mode.

Nationwide Bets

I looked at four bookies: Ladbrokes, PaddyPower, SportingIndex (Spin), Betway. Spin were suspended at the time of inspection. The seats are deduced from the over/under. The Ladbrokes senate majority odds were deduced from Rep>50 (Rep majority), Rep=50 (no majority) and Rep<50 (Dem majority). 

State level Bets

Due to time constraints this will not be considered

Apologia

I am a statistician of the old-school, based in the frequentist and mathematical traditions on limited samples. That stance is being superseded by data science which uses brute-force computer techniques on very-large samples. The latter is good for identifying outliers and perhaps better for gambling, but the former is perhaps better for providing an overview. I hope therefore that you found this article both interesting and informative.

Viewcode

Viewcode is a statistician who spends too much time commentating below-the-line