Opponents of the agreement are equally keen to demonstrate that it doesn't have that level of backing. Our correspondent Gary Duffy considers what outcome the two sides would most like to see.

With eight of the main parties and the British and Irish governments backing the Good Friday Agreement, it would be pretty remarkable if there was not a Yes vote in the referendums on both sides of the Irish border.

But opponents and supporters of the deal both agree the size of the majority could prove very significant in the weeks and months ahead.

The Yes camp is determined to show the deal has a majority in both the unionist and nationalist communities. No campaigners are keen to ensure that doesn't happen.

Making a deal work

Firstly, of course, a large majority is important to give the agreement moral authority, and to ensure that its supporters can move forward to set up the institutions it proposes with sufficient confidence.

For swiftly following on from the referendum will be elections to the new Northern Ireland assembly. If opponents of the deal are able to attract a large No vote in the referendum, they will certainly try to build on that, and win as many seats as possible in 108 strong body.

Their objective then would be make the agreement, and in particular the north south bodies which are a central part of the deal, unworkable.

Spanner in the works

Opponents of the Good Friday Agreement are determined not to give up their struggle even if they lose the vote in the referendum. Their opposition could focus on a range of issues.

They will try to stop any members of Sinn Fein taking up positions as ministers for example. Even unionists who support the deal might be sympathetic to that approach. For votes on sensitive questions in the new assembly a majority is needed from both unionists and nationalists.

The potential for those who wish to create difficulties is enormous.

Getting the vote out

David Trimble

Experts differ on just when the Yes vote will have passed a point which indicates it has won a majority in both the unionist and nationalist communities.

It's been clear for some time that by far the larger part of the nationalist community is in favour of the deal. So attention has focused on unionist intentions, which are crucial for the Ulster Unionist leader David Trimble, a leading supporter of the agreement.

Percentages

Gerry Adams

While the Sinn Fein president Gerry Adams is technically correct when he says that 50% plus one is all that is needed to pass the deal, Mr Trimble certainly wouldn't be in any satisfied with a majority like that.

If the Yes vote passes 65%, then things are improving from his viewpoint, but again, not as much as the Ulster Unionist leader would like. Seventy per cent to 75% is happier territory, while 75% to 80% and he's likely to be claiming victory.

The Reverend Ian Paisley

Over 80% and Mr Trimble will be claiming a triumph that has left opponents like the Reverend Ian Paisley well behind, as figures of the past.

Opposites

The opposite of all this is true of course. Unionist opponents of the agreement want to be able to claim that the deal has not won majority support within their community.

It's likely they would call on the government to start all over again and abandon the deal because it hasn't attracted sufficient backing from both Catholics and Protestants. The government though would be very reluctant to abandon years of work and an agreement in which they have invested so much effort.

The prime minister has personally invested much of his own authority in trying to secure a Yes vote.

Campaign

For much of the campaign it certainly appeared that supporters of the No vote were more self-confident and presenting their case much more effectively. The appearance of IRA and loyalist prisoners at pro-agreement rallies were a public relations nightmare for the Yes camp.