As 2014 draws to a close, the now beleaguered Irish Government has given a commitment to hold a referendum on same-sex marriage in May of 2015. Just over two decades after the legislation that finally decriminalized homosexuality was passed, opinion polls reflect the same meteoric rise here in the acceptance of the rights of gays and lesbians evident in the sweeping legal changes across the western world to ensure against discrimination on the basis of sexual orientation. These polls reveal that approximately 80% of the Irish people favor legalizing same-sex marriage.

This extraordinary response is indicative of just how much this country has changed in the past quarter century. “Catholic Ireland,” while not dead and gone altogether, is in many ways a thing of the past.

Although some of its legacy persists – the pause for the Angelus prior to the RTÉ (Ireland’s national broadcaster) 6:00 PM daily news bulletin and the generous Christmas and Easter holidays aren’t likely to be done away with any time soon – the near absolute power the Church once had has evaporated in the wake of devastating scandals. That it no longer calls the shots is a good thing for a variety of reasons.

Given that the Church’s cries to oppose the upcoming referendum will fall on mostly deaf ears and that the opinion polls are so strongly in favor of marriage equality, is next May’s vote little more than a formality? The short answer to the question is no. I expect that the referendum will be a lot closer than recent polls suggest.

While I do believe that Ireland will probably vote to amend their constitution to allow same-sex marriage and send quite a powerful message in so doing, the final outcome will not be 80%-20%, or anything close to that.

Studies from the US have shown that, on same-sex marriage, there is a “Bradley effect” – the term used to describe the fact that some people deny holding views that may be deemed prejudiced – of approximately 10%. Some voters will change their minds when the campaign starts in earnest.

Others, as happens in every Irish referendum campaign, will vote no for reasons that have nothing to do with the issue they are being asked to decide upon. The young people who most strongly support marriage equality are also the most likely not to turn out on the day of the referendum.

What’s more, two potentially lethal sentiments for marriage equality advocates in the context of a referendum campaign like this one are definitely in the air. The first is a sense of triumphalism.

Some with little experience of politics seem to be taking the result for granted, based on the opinion polls, and view the campaign as an opportunity to humiliate their opponents who they, rightly or wrongly, regard as enemies. Those savvy political operators who will be advising the pro-marriage equality side know that all campaigns should be run as if the candidate or cause were trailing.

They must ruthlessly disown any and all early expressions to the effect that victory is virtually guaranteed.

The second, righteous anger, is more complicated, mainly because it is difficult to argue with people who feel aggrieved at having been treated as less than equal for so long. This righteous anger, however, is often accompanied by standoffishness and a willingness to attack and vilify those who the anger is directed at.

Regardless of how justified, it can alienate that significant segment of the electorate far more concerned about their family’s economic circumstances than the right of gays and lesbians to marry.

By way of example, Irish Times columnist Una Mullally has opined that Irish law “views gays in pretty much the same way as thugs (who viciously assaulted a gay man) on George’s Street do. Furthermore, she has written that: “Our legislation gay-bashes us. Our media gay-bashes us. Our TDs who fight the tide of equality gay-bash us. Religious leaders gay-bash us.” Moreover, she states that the arguments against same-sex marriage have fear at their heart and that she has “never met an argument against gay marriage that isn’t rooted in homophobia.”

There is no denying that her anger is real. A majority would feel it is justified to varying extents. Yet it is likely to turn off a large swathe of voters – who refuse to believe that their parents and grandparents, who go to Mass every Sunday and simply don’t “get” same-sex marriage, have anything in common with those who physically attack gays and lesbians – than to persuade them to amend the constitution.

In fact, this righteous anger has the capacity to perturb undecided and indifferent voters and to render the invariably effective scaremongering tactics that will be employed by the other side even more potent.

The reality is that the global LGBT community has achieved tremendous gains in an extremely short timeframe by emphasizing the very human side of how discriminatory laws have affected them adversely. It has been compelling to hear how people involved in long-term, committed relationships and who wanted to have the same legal recognition attached to their love as to the love shared by heterosexual married couples have been denied it by their governments.

It is positively overwhelming when these people are one’s friends or relatives. Their stories changed the minds of many sceptics who wrongly couldn’t conceive of marriage as anything other than “one man and one woman.” Presidents Obama and Clinton are two converted sceptics. I am another.

In the 2015 same-sex marriage referendum campaign, as another Irish Times columnist, Noel Whelan, has convincingly argued, this unthinking skepticism, as well as fear and homophobia, must be countered “with reassurance and with a passion for equality.” If marriage equality advocates engage accordingly and campaign every day as if they might lose, they will win. If they take a different tack, this referendum could be lost. And that would be a terrible shame.

* Larry Donnelly from Boston lives in Ireland where he is a law lecturer at NUI Galway and regular Irish media contributor on politics, current affairs and law.

Ireland’s same-sex marriage referendum in 2015: How it will be won or lost.Getty Images