The ongoing uncertainty about the type of border that will emerge in Ireland post-Brexit means the possibility of a border poll is increasingly being debated.

Legislation states that a border poll should be held if the Secretary of State for Northern Ireland decides that it is “likely” that such a poll will produce a majority for unification. But what is not specified is how the Secretary of State should make such a judgment.

Undoubtedly one of the key elements are the opinion polls. Along with recent election results, these are, in reality, the only way to gauge current opinion on the Border issue.

Brexit has clearly had an impact. Polls carried out since the referendum have detected two crucial changes

The five most recent opinion polls taken in the North show similar results, with support for the North staying in the UK ranging from 45 per cent to 55 per cent, and averaging around the 50 per cent mark.

But the polls do show differences in support for a united Ireland (depending on the number of Don’t Knows/Not Sures recorded in the polling). This doesn’t mean the polls are wrong, it just shows the current situation is very fluid, and that there is a lot of “changing of minds”, particularly on the pro-united Ireland side.

Polls show differences in support for a united Ireland (depending on the number of Don’t Knows/Not Sures recorded in the polling). File photograph: Getty Images

The differences may also be partly due to the different methods used by individual polls. Some used direct face-to-face interviews, whereas others used online as the research approach. Face-to-face polls usually get higher levels of Don’t Knows/ Not Sures, because many respondents are reluctant to express their real views directly to strangers.

Online polling reduces this “shy voter” effect because respondents are communicating with their own laptop or smartphone and are, therefore, in an environment where they feel more comfortable expressing their real views. This is particularly true when controversial issues are being researched such as equal marriage or the Border.

Elections

Elections are also something a secretary of state will be watching in terms of deciding whether a border referendum should be held. After all, elections involve collating opinions from hundreds of thousands of people. In the most recent elections, unionists have been scoring less than 50 per cent of the vote for the first time in the North’s history, a result in line with recent polls.

Brexit has clearly had an impact. Polls carried out since the referendum have detected two crucial changes in people’s voting intentions on the Border. Traditionally there was a notable minority of nationalist/republicans who were “sort of okay” with the status quo in the North. This group fully supported the 1998 Good Friday agreement, supported devolution, and were pro-EU. Yes, this group still had Irish nationalist aspirations, but they were prepared to wait for a united Ireland. However, post the Brexit referendum, this group has now shifted and become much more assertively pro a united Ireland.

Secondly (and similarly), the vast majority of the Alliance/Green/Others voting block (and, importantly, this is currently about 11 per cent of the voter base) have historically been in favour of the North remaining in the UK. But post the EU referendum, a section of this group has swung to the pro-united Ireland camp, mainly to ensure the North remains within the EU.

Polls are never precisely right, but they’re never totally wrong either

In addition, the number of Don’t Knows/Not Sures in this group has also grown significantly; moving from their original pro Northern Ireland in the UK position.

However, all polls still show a border poll producing a majority in favour of the North remaining in the UK. But the margin is a lot closer than some might expect. On average, the polls show support of the North staying in the UK at around the early to mid-50 per cent (excluding non-voters/ Don’t Knows). The last Northern Ireland border referendum in 1973 produced a 57 per cent majority in favour of staying in the UK.

All polls still show a border poll producing a a majority in favour of the North remaining in the UK. But the margin is a lot closer than some might expect. File photograph: Getty Images

So, according to the legislation, there is currently no basis for calling a border poll.

Remember, polls, like the weather forecast, can give only a broad view of trends and can never be totally precise. After all, when the weather forecast says there will be scattered showers, they can’t tell you the exact time and location of one of those showers. In that sense polls are never precisely right, but they’re never totally wrong either. Also, opinion polls remain the only way public opinion can be gauged on specific issues between elections, and on issues that elections can’t really directly measure, such as the Border. And that’s why the Secretary of State will continue to closely watch what the opinion polls say.

Bill White, is managing director of Belfast-based LucidTalk Polling and Market Research.