Political scientist Paul Fairie
When voters in Britain head to the polls on June 23 to decide whether they want to remain in or leave the European Union (the so-called Brexit referendum), they will be taking part in a vote that will be much more competitive than it seemed it would be several months ago.
When the campaign kicked off back in February, most opinion polls predicted a Remain vote as the most likely outcome. Since then, Remain's lead evaporated and the Leave side took a small and consistent lead in the past few weeks. Now, recent polls suggest the race is evenly split.
Despite this shift in public opinion, Brexit enthusiasts should remain muted in their optimism for victory. While the changes in recent weeks are certainly good signs for those who want Britain to exit the EU, several factors could still tilt the race – however narrowly – back in favour of the Remain side.
There have been significant polling failures in Britain in the past few years. In the runup to the 2015 election, pollsters predicted a tied race between Labour and the Conservatives, with neither party appearing able to win an overall majority. Yet, when the votes were actually counted, the Conservatives won more than half of the seats, besting Labour in the popular vote by more than six percentage points.
Less dramatically, in the weeks before the Scottish referendum, several polls suggested a tightening race, with the final surveys showing about a five-percentage-point lead for those voting against independence. When the result was actually announced, Scotland opted to stay in Britain by a 10-percentage-point margin.
Some of this gap can be explained by sampling error, and perhaps even some last-minute changes in public opinion. Yet, these recent examples give the Remain side some hope that British polling might be regularly under-sampling those who prefer the status quo. Perhaps Conservative voters in 2015 and No voters in the Scottish referendum might have been less motivated to answer an opinion survey than those with a desire for change.
Another wrinkle with British polling is that many surveys fail to include Northern Ireland. This isn't usually a big problem for general election polling, since Northern Ireland has its own parties and only 18 of Britain's 650 seats. Yet, in a close referendum, an area that makes up just under 3 per cent of the population could end up playing an important role. Some polls have suggested that voters in Northern Ireland generally favour remaining in the EU, but polling has been infrequent enough to make it difficult to predict.
The ultimate mystery of every election is the undecided voter, and these voters might hold the key to victory for the Remain side. Several polls released in the past week have shown that between 10 and 15 per cent of voters are still undecided. When this group is pushed to reveal how they are leaning, these same polls show that about 60 per cent of them might end up voting to remain in the EU.
These factors introduce some uncertainty in the small lead pollsters recently showed for the Leave side of the referendum. Other analyses concur with this skepticism. The latest forecast from British opinion polling analyst Matt Singh, who runs the popular blog Number Cruncher Politics and who was one of the few analysts to foretell the polling failure in the 2015 election, estimates that the Remain side is ahead 52 per cent to 48, and sets the probability of a Remain victory at 61 per cent.
Not everything underlying the polls is good news for the Remain side, as the referendum is also a real generation game. Younger voters are strongly in favour of staying in the EU, while older voters are more firmly against. A recent poll by YouGov found that voters aged 18 to 24 wanted to stay in the EU by a margin of 60 to 20, while voters over 65 wanted to leave by a margin of 59 to 30. This gap, which has persisted throughout the campaign, is especially alarming for the pro-EU side, since older voters traditionally turn up to the polls at much higher rates than younger ones.
All told, the age gap and the uncertainties that seem to favour the Remain side can only lead to one sensible forecast: anyone watching the referendum results will be in for a late night.
Paul Fairie is a political scientist in Calgary, where he studies voter behaviour. He helped design an award-winning election-forecasting model with The Globe and Mail.