A Green spoiler effect?

Chris Hanretty considers whether the Green Party are spoiling the Labour Party’s chance of winning the 2015 general election.

Let’s engage in a thought experiment.

Suppose we were able to take all the likely Green votes in each seat, and gift them to the Labour party.

Because this is a thought experiment, we can gloss over whether this scenario is at all realistic. As my colleague Rupert Read (Green Party candidate for Cambridge; other candidates are available) would remind me, Labour doesn’t have a god-given claim on left-of-centre voters. If the Green vote dried up – if candidates across the country stopped campaigning – a good number of these voters would abstain or vote for another party sooner than vote Labour.

But in this scenario, we can ask:

• Where would those votes make the most difference?
• In which seats would the gift of Green votes tip Labour over the edge?

Based on the forecasting work done by ElectionForecast.co.uk, we can identify the seats where Green votes might help Labour win…

In one seat (Brighton Pavilion), Labour win only because the Greens were set to win.

But in seven other seats, Green votes matter.

In Sheffield Hallam and in Cambridge, the Greens might help keep the Liberal Democrats in.

And in Hove and Brighton Kemptown, it’d be the Conservatives that benefit from a Green “spoiler” effect — if that is indeed the right phrase for it.

I wrote at the beginning that this is a thought experiment. The Green vote won’t magically dry up and move to Labour. It might fall back — and indeed, the ElectionForecast.co.uk methodology assumes as much. But the Green vote will remain (probably) large enough to materially affect the outcome in several seats which the Labour party stands a reasonable chance of winning.