The Irish Times/Ipsos MRBI poll published last weekend again showed a large majority in favour of the referendum which the Government proposes to hold next year to allow for those of the same gender to enter into civil marriage. Excluding undecideds, this poll suggests 80 per cent of voters would support such a referendum.

This poll also suggests that the momentum is with the Yes side – this 80 per cent compares to 76 per cent Yes in polls by the same agency last October and 64 per cent Yes in polls by this agency in 2012.

If proponents of this constitutional change want to win, however, they should ignore this and all previous polls on the issue.

Poll data on the question of marriage equality is of very little value at this remove from the referendum. Apart from some politicians, activists and journalists, the public is currently almost entirely disengaged on the issue.

Many of the voters will never care enough either way to vote in the referendum. The turnout is likely to be about 60 per cent. More importantly, most of those who will vote will only engage at or near the end of the campaign.

According to post-referendum surveys conducted by the Referendum Commission, 14 per of those who voted in the 2012 children’s referendum made their mind up on polling day, while a further 44 per cent said they decided how to vote only in the last week of the campaign.

For the Seanad referendum the figures were 12 per cent on the day and a further 35 per cent in the last week.

Polling conducted in advance of large-scale public engagement on a precise constitutional change is entirely unreliable as an indicator of the outcome.

Many of those who are asked by pollsters for a view at this stage are merely giving an instinctive response, one that they feel they should give, or one that will put them in the presumed majority. The argument on this issue is far from over.

Even polls conducted within the last 10 days of referendum campaigns come with strong health warnings. “Seanad referendum set to pass as voters back argument for cost savings” was the front-page headline on this newspaper five days before that referendum in 2013. It was based on an Irish Times/Ipsos MRBI poll which showed 62 per in favour of Seanad abolition. The referendum was defeated 52 to 48.

If one discounts the polls – and at this stage they should be discounted – then the precedents suggest that next year’s marriage referendum is as likely to be defeated as it is to succeed.

Campaigners would do well to remember the following key lessons from previous referendums.

Electorate

The children’s referendum is a more recent case in point. Polls at one stage showed 80 per cent in favour of that referendum but the Yes vote was only 58 per cent on the day.

Another point to note is that referendums proposed by unpopular governments rarely succeed. This is an internationally-recognised phenomenon. Support for the two Government parties combined is measured at just 25 per cent in this week’s Irish Times/Ipsos MRBI poll. Any referendum campaign seen by the voters as led by the Government will be handicapped by the Government’s unpopularity. Hence the need for a broad based non-governmental campaign.

Even extensive support for constitutional change across the parties and across the political spectrum is no guarantor of success. Every member of the Oireachtas except Mattie McGrath TD supported the children’s referendum but the No vote was still 42 per cent.

Social change

Disentangling issues around adoption from the questions of single-gender marriage by early passage of the Children and Family Relations Bill will also go some way to reduce the potential for scaremongering. There appears to be slippage on the timescale for this legislation already, however, which may have a knock-on effect on the timing of the marriage referendum itself.