British voters leaning Leave as Brexit referendum approaches, polls suggest

After months of a "Brexit" looking like a long shot, the United Kingdom might be heading towards that option as the referendum on the country's membership in the European Union finally approaches.

This according to a slew of recent polls. But the margin between the two options on the June 23 referendum ballot — to "remain" a member of the EU or to "leave" it — is very close, and past experience in favour of the status quo suggests the betting odds might still be in favour of a vote to stay.

The referendum is the fulfillment of a promise made by Conservative Prime Minister David Cameron in early 2013, when he pledged to hold a vote on the future of Britain's EU membership if his party was re-elected in the 2015 general election. It was a move designed to head-off divisions within his own party between Eurosceptics and those, like Cameron, who believe the United Kingdom's place is within the EU.

• British pound drops as Brexit support grows
• Trudeau steps into Brexit debates, says Britain should stay in EU

When Cameron announced the day of the referendum in February, polls were showing modest but consistent support for the Remain camp, as they had for some time. But the campaign has begun to lean towards the Leave side in recent weeks.

Support for Remain averaged between 43 and 45 per cent in published national polls conducted in the first four months of the year, maintaining an edge over Leave of between three and four points.

But the past 10 polls published in the U.K. have swung towards Leave, a campaign supported by, among other well-known Conservative MPs, Boris Johnson. The outspoken former mayor of London is one of the front-runners to replace Cameron, who has pledged to resign as prime minister before the 2020 general election.

Over those 10 polls, the Leave option has averaged 44 per cent against 43 per cent for Remain.

This is a big shift from where things stood last year. Throughout 2015, Remain was ahead very comfortably in the polls. In many surveys, the lead was in the double-digits. But fears related to immigration, which spiked after the refugee and migrant crisis that struck Europe last fall, have had a great impact on public opinion and against continued membership in the EU.

As a result, Great Britain's future within the European Union may now be on a razor's edge.

If Britain leaves, maybe Scotland goes too

The debate over Brexit has highlighted some of the divides within Britain.

The Leave campaign's voters skew heavily towards poorer and older Britons, and Conservative and UK Independence Party supporters. The Remain camp, on the other hand, is supported by richer and younger British voters, and those who would cast a ballot for the opposition Labour and Liberal Democrat parties.

The most consequential division, however, may be between Scotland and the rest of the U.K. 

In three recent polls, support for remaining within the EU ranged between 50 and 58 per cent in Scotland, compared to just 35 to 36 per cent support for breaking ties. In England, on the other hand, the margin is nearly as wide in favour of Leave in some polls.

The consequences of Brexit could have a big impact on the future of the U.K.'s unity as well. Though Scots voted 55 per cent in favour of remaining a part of the U.K. in 2014's independence referendum, departure from the EU could be a deal-breaker.

Polls suggest the Yes side in a Scottish independence referendum continues to trail the No camp. The margin stands at about six points. But polls have also indicated that the margin between the two sides would be erased if Great Britain leaves the EU. That could give the impetus needed for the governing Scottish National Party to organize a second referendum on Scottish independence.

Edge to the status quo?

The most powerful element in favour of the Remain campaign is the fear of the unknown. The Leave campaign is asking Britons to cast a ballot for serious, irrevocable and unpredictable change. That can have a dampening effect on voters.

This was demonstrated in 2014's Scottish referendum. Polls taken in the final days of that campaign gave the No side an edge of about five points, rather than the 10-point victory that actually occurred. Something similar happened in Canada in 1995, when the polls suggested that the Oui side was about to prevail in Quebec's sovereignty vote.

This argues in favour of the Remain side getting a boost of a few points at the ballot box. Polls suggest that about 12 per cent of voters remain undecided, and a large proportion of them may plump for the status quo when push comes to shove.

But that assumes turnout will be high. If turnout is lower, angrier Leave voters — being older, they are a cohort that votes in big numbers — may be more motivated to cast a ballot.

The betting markets still expect voters to side with the European Union. But that bet may be getting riskier by the day.

• The Pollcast: Subscribe to Éric Grenier's podcast
• ​Trudeau's Liberals hold support from post-election honeymoon

Listen to CBC Radio's The House at 9 a.m. (9:30 NT) on Saturdays. Follow on Twitter @CBCTheHouse.