Yes campaign: repealers have taken a softly-softly approach to their pitch to the middle ground. Photograph: Charles McQuillan/Getty No campaign: a major pivot that would see anti-abortion campaigners address the middle ground was expected but has not materialised. Photograph: Artur Widak/AFP/Getty

RTE presenter Claire Byrne had to ask members of the audience to 'refrain from calling people liars' after many heated exchanges between audience and panel members. Video: RTE

If there is to be a move in the abortion-referendum campaign, then this is moving week.

A slew of polls early in the campaign painted more or less the same picture: a substantial lead for the Yes side, and a pretty solid foundation for that support. That lead is not unassailable, and a dramatic late swing to the No side, of the sort we have seen in other referendum campaigns, could change the outcome.

If that is to happen it is likely to happen in the next seven days, as undecided and weakly committed voters begin to make up their minds. If the No side is going to turn it around it needs to make some headway, and fast.

So tonight’s debate on RTÉ television is an important moment in the campaign. Several hundred thousand people will be watching, and many of them will be the kind of swing voters who will decide the result of the referendum to repeal the Eighth Amendment to the Constitution, which bans abortion in almost all circumstances.

It is those middle-ground swing voters whom the No side will have to target in the remaining days of the campaign if the current trajectory is to change. There is little sign that it is doing so with any purpose or success, however. Many of its posters and messages have been more directed at its base, the 30 to 35 per cent of voters who do not want constitutional change, rather than at the chunk in the middle who want change but are not sure if they want it to be to the extent the Government has proposed. It is important to get your base out in any election or referendum, but there are simply not enough in the anti-abortion base to win this referendum. Related Total of 6,666 abortions carried out under new legislation last year

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All individual polls are susceptible to error; taken together, dozens of them rarely are. And, combined, all the polling of the past 18 months and before tells us that a settled majority of Irish voters is in favour of liberalising the law on abortion; the majorities for legal abortion in the “hard cases” of rape, fatal foetal abnormalities, threats to the health of the woman and so on are huge. They will not change. That is a great advantage to the repealers.

The retain side can win only if it convinces enough soft repealers and undecided voters that the Government’s proposal to legalise abortion on request up to the 12th week of pregnancy is a step too far. But those soft repealers are not responsive to the uncompromising abortion-is-murder message that has underpinned much No side campaigning. If you are talking about dead babies you are not talking to the middle ground.

A major No side pivot that would see it address the middle ground was expected but has not materialised. Not yet, anyway. Facebook and Google’s decision to restrict and cancel referendum advertising disproportionately affected the No side. It has made the pivot harder.

It has also angered No campaigners, feeding their sense that the establishment – the Government and the media – is ranged against them. And when you are angry it’s harder to talk to the middle ground.

By contrast the Yes side has been better at taking a softly-softly approach to its pitch to the middle. It has talked about the hard cases, about the realities of women’s lives, about lived experience. It is easier for the repealers to talk to the middle ground, because they have more in common with them. But they have also been better at it than their opponents have. The campaign has by and large cultivated a message discipline and focus largely absent from its early stages (and still wholly absent online, although that may not matter).

None of this means there can’t be a change in the campaign as it enters its final stage. But it does mean it is hard to see where it would come from. For now, anyway, it’s advantage repeal.

Claire Byrne Live Referendum Special is on RTÉ One from 9.35pm