Election forecasting

UK Opinion Poll Tracker #3 – 28th April 2017

April 30, 2017 By Nigel

The Prime Minister has called for a General Election on 8th June 2017 and parliament has approved this. For the next 6 weeks, opinion polls will be coming in thick and fast and I will do my part by keeping my opinion poll tracker up to date and explaining what the latest trends are. I will use these trends to update my 2017 General Election Seat Predictions and you should read that post in conjunction with this one.

The latest situation is that the Conservatives hold an 18% lead over Labour and are on track for a working majority of 171 seats. Labour are set for their worst general election vote share since 1918 and the Lib Dems have overtaken UKIP to regain 3rd place in the polls for the first time since December 2013.

By-Elections #2 – Review of Copeland & Stoke Central predictions

February 24, 2017 By Nigel

The results are in and it is now time to review my predictions of the Copeland and Stoke-on-Trent Central by-elections. How well did my by-election model do and what lessons can be learnt? Let’s look at the numbers first.

By-Election Forecast #2 – Stoke-on-Trent Central, Staffordshire

February 19, 2017 By Nigel

Originally posted on 19th February 2017. I then added an updated forecast on 22nd February which can be seen at the bottom of this post.

If UKIP want to supplant Labour in the North England, they must win Stoke-on-Trent Central to kickstart this trend and the odds are 2 to 1 that they will win. That is my forecast after running my by-election model on Stoke-on-Trent Central. For more details about the methodology, please read my description of how I forecast by-elections in the Brexit era.

My model uses both the breakdown of the 2015 General Election results when Labour held the seat with a 16% majority on a 50% turnout (the 2^nd lowest turnout in the whole of the UK in 2015) and the 2016 EU referendum result where I estimate that Leave won with 71% of the vote on a 60% turnout. This makes this seat the 17^th most Leave seat in the UK and it is worth noting that its two neighbours were #22 (Stoke South) & #3 (Stoke North). In % terms, the increase in number of voters in 2016 was the 22^nd highest in the UK and has created a substantial Non-GE segment of 17% of 2016 voters that have the potential to influence the by-election. Whether these non-voters from 2015 will vote in the by-election is one of the big uncertainties and it will be fascinating to see if they do.

By-Election Forecast #1 – Copeland, Cumbria

February 19, 2017 By Nigel

Originally published on 19th February. Please scroll to the bottom for an updated forecast as of 22nd February.

The Conservatives are well set to take Copeland from Labour. That is my forecast after running my by-election model on Copeland. According to Matt Singh of NCP Politics, the last comparable by-election would be in 1878! For more details about my methodology, please read how I forecast by-elections in the Brexit era.

As always, we need to start with a breakdown of the 2015 General Election results when Labour held the seat with a 6% majority and the 2016 EU referendum result where I estimate that Leave won with 61% of the vote.

By-Elections #1 – How to predict outcomes in the Brexit era

February 19, 2017 By Nigel

Since the UK voted to leave the EU on 23^rd June 2016, there have been 3 contested parliamentary by-elections (Witney, Richmond Park, Sleaford & North Hykeham) and one uncontested by-election (Batley & Spen which was the late Jo Cox’s seat). Many commentators have analysed these results to see how the referendum result has impacted on parliamentary voting intentions. Whatever voter dynamics are revealed, it is reasonable to assume that they are likely to influence future by-elections. In late October 2016 just after the Witney result, I realised it could be possible to build a by-election model by combining two sources of data.

My own estimates of the Leave & Remain votes in each of the 650 parliamentary constituencies where I calculated that 400 out of 650 seats voted Leave.
My interpretation of the Lord Ashcroft “exit poll” carried out on 21^st to 23^rd June 2016 and published immediately after the results were announced.

At the time, I described my by-election modelling approach in a youtube clip and that is worth listening to. I have made some changes to my model since then so this post is the most up to date version of my model. I will illustrate the basic principle using the Witney by-election (David Cameron’s former seat) of 20^th October 2016 where the top line numbers are: