The decision of Gerry Adams to step down as leader of Sinn Féin next year after 35 years in the post has huge implications for the future of politics North and South.
The final phase of his leadership will test whether Adams is serious about a shared future for the two communities in Northern Ireland or whether the aspiration for a united Ireland has made the Belfast Agreement redundant as far as Sinn Féin is concerned.
If the power-sharing institutions in the North are not restored by the time he departs, it is difficult to see how a successor will be able to put them in place for the foreseeable future.
A failure by Sinn Féin to cut a deal in the North will help to confirm the taunts of its opponents in the Republic that it is not serious about taking on the responsibilities of power on either side of the border.
The departure of Adams will be a defining moment for the prospects of his party south of the border. While Sinn Féin has become a serious force in the Republic since the Belfast Agreement of 1998, its progress appears to have stalled with the revival in the fortunes of Fianna Fáil.
The continued presence of the 69-year-old Adams, and all his associations to the violent years of the Troubles, has been widely regarded as an obstacle to the party’s ambition to get into government in Dublin, but his departure will not necessarily change things.
For a start many Sinn Féin members do not appear to have any desire to put the past behind them. One of the biggest cheers of the ardfheis weekend came during a special half-hour tribute to Martin McGuinness, when Elisha McCallion, the MP for Foyle, declared: “Martin was a proud member of the IRA.” It led to rapturous applause, cheering and thunderous stamping of feet.
Mary Lou McDonald, regarded as the most likely successor to the leadership, has never resiled from the party’s past and has strongly defended the Provisional IRA campaign of violence whenever the issue has arisen.
Fianna Fáil leader Micheál Martin hammered home this point in a speech on Saturday night, saying that all of the potential new Sinn Féin leaders joined the party before the ceasefires and had repeatedly defended the Provisional IRA's campaign. Martin reiterated the commitment that he will not lead his party into coalition with Sinn Féin in any circumstances.
This is the nub of the challenge facing the new Sinn Féin leader. Fianna Fáil and Fine Gael have ruled out coalition with the party after the next election regardless of what the numbers in the Dáil happen to be.
That will leave Sinn Féin in a battle to stay relevant during the next election campaign as the political debate begins to focus on who will be in government.