Micheál Martin is in a position no other Opposition leader in the history of the State has occupied. It is within his power to determine the date of the next general election.
How Martin and Fianna Fáil use that power will have a critical bearing on the success – or failure – of the 32nd Dáil.
The next 100 days will provide some vital clues about how Fianna Fáil intends to use its leverage. By the time we get to November we will either have a budget for 2017 in place or we will be in the middle of another election campaign.
Most people in Leinster House expect that the Fine Gael-led minority Government will be able to get the budget through the Dáil, but the manner in which that is achieved will tell its own tale.
Under the terms of the "confidence and supply" arrangement that enabled Fine Gael to retain office, Fianna Fáil agreed to facilitate budgets consistent with the agreed policy principles of the document that complied with domestic and EU fiscal rules.
On the face of it, that means Fianna Fáil will have to accept the basic arithmetic underpinning the budget and all of the key figures.
While there may be some quibbles about individual items, the two parties will have ample time to iron out any potential glitches before Michael Noonan and Paschal Donohoe present their tax and spending packages to the Dáil in October.
In the process of negotiating the programme for government, Fianna Fáil extracted a pledge from Fine Gael that there would be at least a 2:1 split favouring investment in public spending over tax reductions.
That formula will underpin the budget. While neither party to the agreement has any incentive to breach it there may well be arguments about the fine detail which could lead to some brinkmanship in the run-up to Budget Day.
However, as it is clearly not in Fianna Fáil’s interest to bring the experiment in minority government to a sudden halt, the expectation is that the budget will go through even if there is a bit of drama during the run-in to it.
‘New politics’
Martin has a lot riding on making the “new politics” work. He rejected coalition with Fine Gael and the prospect of being taoiseach in a rotation deal on the basis that it was in the best long-term interests of his party and the country to eschew the perks of office for the present at least.
That has placed a heavy responsibility on him to make the deal with Fine Gael work, and he has pledged himself to undertake the responsibilities of Opposition in an entirely new way.
While there were a couple of rocky moments in the first 100 days of government as Fine Gael and Fianna Fáil got used to the new arrangement, the two parties appear to be getting to grips with the requirements of the other.
Fianna Fáil TDs have generally been more comfortable with the arrangement, particularly as it has allowed them some victories in Dáil votes that would have been impossible under the old rules of the game.
Fine Gael has been slower to appreciate the nature of the deal with some of its backbenchers annoyed at the room for manoeuvre being given to Fianna Fáil but the resentment is beginning to abate.
It took Fine Gael some time to appreciate that Fianna Fáil had to have some victories to its credit, not just in the programme for government where it insisted on winning, the argument over water, but also on some high-profile Dáil votes.
Fianna Fáil's decision to back a Labour motion on workers' rights including a significant increase in the minimum wage was a case in point. The Government suffered a humiliating defeat, and some Fine Gael Ministers were furious until Enda Kenny calmed them down.
The working relationship between the Taoiseach and the Fianna Fáil leader has been critical to the success of the experiment and so far the two appear to have established a basis of trust.
Debates
The budget, though, will be the real test. Fianna Fáil will have to agree to the basic arithmetic set out by Noonan and will not be able to indulge in the Opposition grandstanding that was a normal feature of budget debates.
What will make that difficult is that Sinn Féin and those on the hard left, as well as a variety of non-Government Independents, will try to make as much political capital as they can by forcing Fianna Fáil to underpin the more unpopular aspects of the budget in Dáil votes.
Still, what will give Martin the confidence to proceed is that opinion polls since the Government was formed have shown Fianna Fáil to be the most significant beneficiaries of the new arrangement with the standing of the party and its leader enhanced by the new politics.
Absorbing the jibes from its rivals on the Opposition benches has been made more palatable by the fact that the public seems to be quite happy with the Fianna Fáil tactic.
A move to end the arrangement abruptly and precipitate an early election could prove counterproductive. Fianna Fáil’s rise in the polls could quickly go into reverse if the party were deemed responsible for an unnecessary election.
Martin and his colleagues are no doubt acutely aware of this and they also know that if the budget for 2017 is passed, the pressure will be off for another 12 months, barring unexpected events.
During that period an entirely new process for devising budgets in consultation with the Opposition parties will be put in place so that next year’s measure will emerge in a very different way.
That will provide its own challenges but for the moment at least Fianna Fáil is in the happy position of having it both ways.
