Days before a referendum that seemed to be in the bag for David Cameron, a YouGov Plc poll suddenly showed the Leave side ahead.
The pound plunged, the prime minister panicked — then Scotland voted to stay in the UK by a 10-point margin.
Two years on, and UK voters are preparing to decide whether to leave the EU on June 23.
The question for politicians and pollsters studying the current referendum is whetherpolls showing Leave in the lead, including ones from YouGov and TNS yesterday, are just a symptom of another wobbly weekend before a clear Cameron victory or a sign that his luck has run out.
Pollsters aren’t much help. Having been burned in last year’s UK general election, when they failed to predict that the Tories would win a majority, many have doubts about the reliability of their work on the referendum.
Sterling fell last week when ICM published online and telephone polls both showing Leave ahead. It fell further yesterday after YouGov put Leave at 45% to 41% for Remain and TNS had the Brexit camp ahead by 43% to 41%.
“It’s hard to think of a more bewildering electoral event,” said Martin Boon, a director at ICM.
“The polls have not really moved, and more phone polls of late, with their pro-Remain tendencies, have added to or created the narrative that Remain might cruise it. But that could be a false narrative, and for me the only correct thing to continue to say is: I just don’t know how this will go.”
A year-long inquiry into the May 2015 UK election polling failure concluded that the main problem was unrepresentative samples, and that this would be hard to fix.
Instead, the inquiry urged the public to be more sceptical about polling. If more reason were needed to doubt the EU referendum polls, they don’t even agree on a picture. Online polls have tended to show the two sides tied, while telephone ones have generally put Remain ahead.
“There’s a discrepancy in levels of motivation,” said Joe Twyman, head of political polling at YouGov.
“There are millions of people who would walk barefoot across broken glass to vote to leave. The Remain campaign doesn’t have people who feel the same way. I still think we’ll vote to stay, but that’s assuming that there’s a move towards the status quo in the final days.”
The pro-EU camp’s core message is that a Brexit will make the UK poorer. Yet 58% of respondents to an Ipsos Mori poll published last week said they didn’t think leaving the EU would affect their own standard of living — indicating the government’s message has yet to get through.
But some pollsters are less uncertain. Tom Mludzinski, director of political polling at ComRes, is more confident of a Remain win.
Oddschecker has the implied probability of a Brexit rising to almost 31% yesterday morning, up from a low of 19.7% on May 26. Matt Singh, polling analyst at NumberCruncherPolitics, had the probability at almost 22%.