Who will win? Make your prediction. Photo: Charlie Morris/May2015
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Follow every prediction – and make your own – with May2015’s election-forecasting machine

50 years after the BBC and ITN competed to predict election night first, we launch Florence: our election-forecasting machine.

How do you make sense of the most unpredictable election ever? We’re trying. For a while now we’ve been tracking all the latest polls – from the daily stream of national polls to Lord Ashcroft’s batches of seat surveys.

The challenge is turning abstract polls into actual seat predictions for each party. There are 650 elections on May 7, not one big one. In the past forecasters would plug polls into a nationwide swing model – usually uniform swing – but such swingometers are limited in a six-party system.

So we’ve developed a simple model. The Greens, Scotland and Ashcroft are now all fully integrated into our prediction, which we make in two steps. First, we work out what the national polls imply will happen in every seat (by using a slightly more sophisticated model than uniform swing), and then we separate any seats Lord Ashcroft has polled.

The Greens, Scotland and Ashcroft are now all fully integrated into our modelMake your own prediction.

He is polling the election’s most marginal – or closely fought – seats. They will decide the election. We plug them into our model, and then adjust them as national polls change.

This two-step process is shown below. You can see the current national polls hand both Labour and the Tories around 230 seats. These are effectively the election’s “safe” seats – excluding Scotland, which Ashcroft is in the midst of polling for the first time. (We now distinguish between GB-wide and Scottish polls, and you can make your own predictions for each.)

We then add in Ashcroft’s polls. He has published 112, and put Labour ahead in twice as many of them as the Tories.

Some pundits, especially Tory ones, have dismissed these leads – a good bulk of which Labour amassed before their faltering end to 2014. But these polls aren’t static; every day they adjust in line with the national polls. If the Lib Dems surge or Tories collapse in national polls, Ashcroft’s seat polls from last summer will change too.

Other forecasts

As we have discussed before, we are working with limited data (far more limited data, in a more complicated system, than exists in the US). Without more billionaires, predicting British elections will remain guesswork. And we aren’t replacing other forecasts – we are gathering them all together. You can now stay up-to-date with the predictions of Stephen Fisher, Election Forecast and Electoral Calculus on May2015 – as well as Ladbrokes’ latest odds.

A new academic forecast, from the team behind Polling Observatory, will shortly launch on May2015.

Each model offers something different. Fisher and Election Forecast are predicting what will happen in May. We are avoiding extra assumptions and predicting what would happen in an election held today. As we approach the election, the assumptions built into their forecasts (namely a move towards the Tories) will become less important, and every model will increasingly rely on the polls.

Fifty years of forecasts

Machines have been predicting elections since the 1950s, when the BBC’s “Ella” and ITN’s “Deuce” computers duelled on election night in 1959. More recently, Nate Silver famously forecast the 2012 US Presidential election, before the New York Times replaced him with their “Leo” computer.

55 years after Ella, we’ve nicknamed our model “Florence”, after the woman who pioneered not just healthcare, but data journalism. Her coxcomb graphs of the Crimean War – made a century before the first BBC election nights – showed how army conditions killed far more British soldiers than conflict did. She was one of the first campaigners to enlist vivid and simple graphics in making arguments.

May2015 is the New Statesman's new elections site. Explore it for data, interviews and ideas on the general election.

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The biggest divide in politics is not left against right, but liberals against authoritarians

My week, including a Lib Dem membership rise, The Avalanches, and why I'm putting pressure on Theresa May over child refugees.

It is a boost for us that Nick Clegg has agreed to return to the front line and be our Brexit spokesperson. I hadn’t even had a chance at our meeting to make him the offer when he said: “Before we start, I’ve been thinking about this and want to take on the fight over Europe.”

With Labour apparently willing to give the Tories a free pass to take us out of Europe, the Liberal Democrats are the only UK-wide party that will go into the next election campaigning to maintain our membership of the EU. The stage is remarkably clear for us to remind Theresa May precisely what she would be risking if we abandon free trade, free movement, environmental protection, workers’ rights and cross-border security co-operation. More than a month on from the referendum, all we have heard from the Tories is that “Brexit means Brexit” – but they have given us no clue that they understand what that means.


Premature obituaries

Not long ago, the received wisdom was that all political parties were dying – but lately the supposed corpses have twitched into life. True, many who have joined Labour’s ranks are so hard left that they don’t see winning elections as a primary (or even a desirable) purpose of a party, and opening up Labour to those with a very different agenda could ultimately destroy it.

Our experience has been happier: 20,000 people joined the Liberal Democrat fightback in the wake of the 2015 general election result, and 17,000 more have joined since the referendum. We now have more members than at any time this century.


Breaking up is hard to do

Journalists have been asking repeatedly if I want to see the break-up of the Labour Party, with moderates defecting to the Liberal Democrats. I have been clear that I am not a home-wrecker and it is for Labour to determine its own future, just as I focus on advancing the Liberal Democrat cause. Yet I have also been clear that I am happy for my party to be a home for liberals of whatever hue. I enjoyed campaigning in the referendum with a variety of progressive figures, just as moderates from different parties shared platforms in 1975. It struck me that far more unites us than divides us.

That said, not all “moderate” Labour figures could be described as “liberal”, as John Reid demonstrated as Labour home secretary. The modern political divide is less left v right than authoritarian v liberal. Both left and right are looking increasingly authoritarian and outright nasty, with fewer voices prepared to stand up for liberal values.


What I did on my holidays

Time off has been virtually non-existent, but I am reading A Wilderness of Mirrors by Mark Meynell (about loss of trust in politics, the media and just about everything). I’m also obsessively listening to Wildflower by the Avalanches, their second album, 16 years after their first. It’s outstanding – almost 60 minutes of intelligently crafted dialogue, samples and epic production.

During the political maelstrom, I have been thinking back to the idyllic few days I spent over half-term on the Scottish island of Colonsay: swimming in the sea with the kids (very cold but strangely exhilarating ­after a decent jog), running and walking. An added bonus is that Colonsay is the smallest island in the world to have its own brewery. I can now heartily recommend it.


Preparing for the next fight

The odds are weirdly long on an early general election, but I refuse to be complacent – and not merely because the bookies were so wrong about Brexit. If we have learned one truth about Theresa May as Prime Minister so far, it is that she is utterly ruthless. After her savage cabinet sackings, this is, in effect, a new government. She has refused to go to the country, even though she lectured Gordon Brown on the need to gain the endorsement of the electorate when he replaced Tony Blair. Perhaps she doesn’t care much about legitimacy, but she cares about power.

You can be sure that she will be keeping half an eye on Labour’s leadership election. With Jeremy Corbyn potentially reconfirmed as leader in September against the wishes of three-quarters of his MPs, Mrs May might conclude that she will never have a better chance to increase her narrow majority. Throw in the possibility that the economy worsens next year as Brexit starts to bite, and I rule nothing out.

So, we are already selecting candidates. It is vital that they dig in early. As we are the only party prepared to make the positive case for Europe, such an election would present us with an amazing opportunity.


Sitting Priti

David Cameron pledged to take an unspecified number of unaccompanied children from camps across the Continent. I am putting pressure on Theresa May to turn that vague commitment into a proper plan. Having visited such camps, I have been fighting for Britain to give sanctuary to a minimum of 3,000 unaccompanied children, who are currently open to the worst kinds of exploitation. We have heard nothing but silence from the government, with underfunded councils reporting that they are not receiving the help they need from Whitehall.

Meanwhile, it remains government policy to send refugees to Turkey – whose increasingly authoritarian government has just suspended human rights protection.

As if all of this were not grim enough, we have a new Secretary of State for International Development, Priti Patel, who has said that she thinks aid should be used largely to promote trade. As someone who wants our country to be respected around the world, I find this plain embarrassing. Actually, it’s worse. It’s shaming. As with Europe, so with the world: the ­Conservative government is hauling up the drawbridge just when we need more than ever to engage with people beyond our shores.

Tim Farron is the leader of the Liberal Democrats. To join the party, visit: libdems.org.uk/join

Tim Farron is leader of the Liberal Democrats.

This article first appeared in the 28 July 2016 issue of the New Statesman, Summer Double Issue