Final election polls show widening Tory lead, but survey doubts remain

As Britain heads to the voting booths, most opinion polls showed a solid lead for the Conservative party as the recent narrowing over Labour eased, though doubts remain over the accuracy of such surveys after major misfires in recent years.

Following a breathless final day of campaigning to voters by Theresa May and Jeremy Corbyn, Thursday morning saw the last opinion poll published, with Ipsos MORI giving May's Tories a larger lead of 44%-36% over Corbyn's Labour than its previous prediction of 45%-40% last week. Ipsos had the Liberal Democrats on 7%, Greens on 5% and Ukip on 4%.

YouGov's final poll for The Times on Wednesday night also gave a bigger Conservative lead, with the party remaining unchanged on 42% while Labour fell three points to 35%. The Liberal Democrats were on 10%, Ukip on 5%, Greens on 2% and others 6%.

The last poll by ICM for the Guardian put the Conservatives ahead by 12 points, up one point to 46% while Jeremy Corbyn's Labour’s stayed at 34%.

The ICM result indicated May will have a House of Commons majority of 96 on Electoral Calculus estimates, which is short of the widely predicted landslide six weeks ago but not the number Labour supporters were hoping for after the strong momentum Corbyn's campaign had built up in recent weeks.

For ComRes the Tories were down three points and Labour down one to make it 44%-34%, while Panelbase had both top parties unchanged at 44%-36% and TNS had Labour up five points to close the gap on the unchanged Tories to 43%-38%.

Survation had the both main parties up one point for the closest call at 41%-40%.

MAY'S MAJORITY

Prime Minister May had a House of Commons majority of 10 seats when she called the snap election in April, with 330 seats out of the total of 650.

Conservative confidence at the time saw projections of a swelling of this majority to well over 100, with some projections north of 150.

Despite significant narrowing of the lead by Labour in the weeks since, Chris Hanretty of the University of East Anglia forecast the Conservatives would still gain a strong majority in Parliament.

Thanks to seat gains in the North of England and Scotland, he reckons May will benefit from a swing of 45 seats and end up with 375 MPs in Parliament.

Based on their optimism two months back, this would is a disappointing outcome for the Tories and could even see a leadership challenge disrupt the Brexit talks.

“Anything less than a 50 seat majority looks like a gamble that’s not paid off and it would make it less likely she’ll contest the next election,” Andrew Russell, professor of politics at the University of Manchester, told Bloomberg on Thursday. “If you’re a European leader right now, you look at this car crash and think she’s going to have to swallow this pretty hard.”

IN POLLS WE TRUST?

The various polls therefore show the Tory lead varying between one point and 12 points. After polls for the 2015 UK election and US presidential race were widely derided, there remains a strong element of distrust despite ongoing efforts by polling companies to improve their methods and models.

Polling expert Jansev Jemal in Dods Research noted that a poll or survey is not a census, they are the result of talking to a small proportion of the entire population.

"A typical poll of 1,000 people usually has a margin of error of plus or minus 3%. This means that if a poll is showing a party as having 30% support, support for the party in the total population might be anywhere between 27% and 33%. This is likely to be the case 95% of the time, but 5% of the time the “true” figure may fall outside of this range," he said.

Professor John Custice, Strathclyde University's oft-quoted polling guru, noted this week the crucial statistic to keep in mind was that at in 2015 election the Conservatives were seven points ahead of Labour in the national vote and that secured them an overall majority of 12.

"So, any poll that puts the Conservative lead at six points or less is suggesting that the Conservatives will be less far ahead of Labour than two years ago - and, consequently, could potentially be at risk of losing their overall majority," he said in a BBC article. "Conversely, any poll that reckons the Conservatives are ahead by eight points or more implies that the party is likely to make gains from Labour and thus increase its majority."

FINAL ALTERATIONS

While the seven point Conservative lead predicted by YouGov's final 42%-35% opinion poll is the same as was the final result in the 2015 election, the pollster said it believes it is likely May will be returned with an increased majority in the House of Commons.

The online polling company, which has been an outlier for its constituency poll that predicted a hung parliament, said it was finding the Tories were outperforming in Scotland and forecast May's party win "a good handful of seats" from the SNP and perform disproportionately well in Labour-held seats that voted for Brexit.

YouGov also made some changes to its method for its final poll: "The first is that rather than asking people which party they’d vote for, we showed respondents a list of the people actually standing in their constituency and asked which one they would vote for. Hopefully this will help pick up any tactical vote considerations and remove any issue of people saying they would vote UKIP or Green in seats where UKIP or the Greens are not actually standing."

Secondly, it reallocated respondents who say "don’t know", but who also say they are very likely to vote: "We assume uncertain voters who say they “don’t know” at this stage won’t actually vote, but those who say they are 8+/10 certain to vote we have reallocated back to the party they voted for in 2015."

The Guardian noted that detail of the ICM poll confirmed Corbyn’s popularity among younger voters with a lead of 66%-23% versus the Tories among 18 to 24 year olds and 47%-33% among 25 to 33 year olds.

ICM found the declared intended turnout of both these younger age groups at 64% and 70% was points below other age groups

As for ICM, company spokesman Martin Boon said: “This final poll confirms the pattern that ICM has produced over the last fortnight: a fairly healthy and static Conservative share with consolidation of the Labourbump first witnessed after the manifesto publication”.