One of the major obstacles in the way of any coalition involving Fianna Fáil in the event of a hung Dáil is the requirement that the party must convene a special ardfheis to approve a coalition deal with another party.

New rules laid down in 2012 specify that a draft programme for government must be presented to the members of the organisation at a special ardfheis before any coalition arrangement can proceed.

The rule specifies that all of those attending the ardfheis will be entitled to vote and a simple majority will be required to approve a draft programme for government.

“There is no way that our members would agree to allow us to enter a coalition with Fine Gael as a minority party and probably not even as a majority party in a coalition,” said one leading member of Fianna Fail this week. “That is why we are ruling out coalition with them.

“As far as our members are concerned,” he added, “to go in as the junior partner of Fine Gael would spell the death knell of the party and they are simply not prepared to do it.”

As well as antipathy to going into government with the party it has opposed for 90 years, there is also a strong view in Fianna Fáil that it would be bad for Irish democracy for the two old enemies to go into office together.

“If that happened, you would have a centre-right government facing an opposition led by Sinn Féin and the hard left,” another Fianna Fáil source said. “They would then become the alternative government and the long-term consequences for our society could be dangerous.”

Supporting a Fine Gael-led minority government from the outside is a different proposition. For a start, it would be a decision for the Fianna Fáil parliamentary party and not for the membership.

In any case, it would not provoke anything like the same level of hostility from the party members as entering a coalition with Fine Gael.

Former Fianna Fáil minister Dermot Ahern suggested last week that his party owed it to the country to do a reverse of the Tallaght strategy adopted by Fine Gael leader Alan Dukes in 1987, when he allowed Charles Haughey’s minority government to get its budgets and essential legislation through the Dáil.

Fianna Fáil would be likely to lay down more stringent conditions about what it would and would not support, but party sources emphasised that whatever happened, they would act responsibly and that continued political and economic stability would be an important consideration.

The record of junior coalition partners in Irish politics is one of the principal reasons for the deep suspicion of coalitions in the current Fianna Fáil parliamentary party.

The extinction of the Progressive Democrats after its coalition with Fianna Fáil in 2007 is still a vivid memory. Having had three successful terms in coalition between 1992 and 2007, the PDs bit the dust in an election where its senior coalition partner, Fianna Fáil, did well and returned to government.

The poor performance of the Labour Party each time it has faced into election as part of an outgoing government has also sparked anxiety in Fianna Fáil about joining a coalition as a junior partner.

Fianna Fáil entered coalition for the first time in 1989 with the Progressive Democrats, having made rejection of it a “core value” for the previous 60 years. The episode proved traumatic for the party and led to the split that eventually resulted in the departure of Charles Haughey as taoiseach and his replacement by Albert Reynolds, who had described coalition with the PDs as “a temporary little arrangement.”

Ironically, less than a year after taking office, Reynolds entered a coalition with Labour, which was much more of a partnership government, with six of the 15 cabinet positions going to the junior partner.

That coalition, which almost all commentators forecast would last for a decade, crumbled after two years but in the long term, it did not do Fianna Fáil any harm and it bounced back to office in 1997. It stayed in power in coalition with the Progressive Democrats (twice) and the Green Party (once) before the meltdown of 2011.

Since the 1980s, Labour has had the formula now being followed by Fianna Fáil that any coalition deal has to be approved by the party members at a delegate conference. At times, that has led to fractious debates but the members have always backed a deal negotiated by the leadership. The Greens also follow the same formula.

By contrast, the Fine Gael parliamentary party has the right to sanction a coalition arrangement and a programme for government and there is no requirement for a delegate conference.

Day-to-day decisions in Sinn Féin are made by the party’s ardchomhairle (national executive) and it will make the decision on whether or not to enter coalition should the occasion arise.