The virtuous circle is now in reverse. The engine of the peace process had been electoral success. The more the parties of the extremes were willing to engage with the core ideas of power-sharing and reconciliation, the more people voted for them. That reality kept them at it, for there is nothing a political party wants more than votes.
Both Sinn Fein and the DUP resisted this and had to be drawn deeper into the peace process until that reality was plain to them.
Sinn Fein, at the start, wished above all to preserve the legitimacy of the IRA campaign.
It indulged the idea that a reformed police service would absorb members of the IRA at the ranks they had held there.
Republicans resisted the consent principle. Sinn Fein demanded that the British Government would become persuaders for Irish unity.
Even once the talks had started in 1997, the party was briefing that the creation of a Northern Ireland Assembly was not an outcome it was working towards.
But having argued for years that the IRA was a democratic people's army, it saw plainly now that the people wanted peace and would support it in greater numbers if the end of the Troubles was on offer.
Similarly, the DUP had to be dragged kicking and screaming into the process, and at a later stage.
The Rev Ian Paisley had rejected the Good Friday Agreement and campaigned on, not just for the acceptance by Sinn Fein of the police but for repentance and the verifiable decommissioning of weapons.
In 2004 he wanted 'sackcloth and ashes'.
The IRA wanted to continue reaping in huge bounties from daring robberies and Sinn Fein provided cover.
But after the St Andrews Agreement and the Sinn Fein assent to policing, Paisley joined forces with Martin McGuinness and Sinn Fein and the DUP agreed to govern Northern Ireland together.
This would not be without glitches and further threats to the institutions.
The DUP threatened to pull them down over the OTR scheme which assured more than 200 IRA men on-the-run that they could come home.
One of them was promptly charged with the 1982 Hyde Park bombing and a court ruled that he would have to be released because of the note he had been given.
Sinn Fein threatened to pull down Stormont over the welfare cuts which it refused to implement, and for which mitigation was agreed.
But the fundamental reality for both was that if they demonstrated a willingness to make power-sharing work, the electorate would stay with them, subject to another painful reality; that much of the electorate was getting bored.
Both parties had been facilitated by a toxic clause in the St Andrews Agreement which changed the fundamentals of Good Friday.
This said that the First and Deputy First Ministers would be chosen from the biggest parties, not the biggest communities. This provided a huge incentive for voters to discard the Ulster Unionist Party and the SDLP, which they did.
For Sinn Fein and the DUP, this was a gift. But they both seemed to need to test popularity with their bases.
While they were harvesting new votes from people who were not adamant true believers in the old cause, they behaved as if they felt they had to provide assurance to those who had been with them all along - the hardliners.
Each big party felt its heart pulled two ways, into power-sharing and agreement and back towards the ghetto mentality.
The virtuous circle worked to keep them on track, side by side, rewarded by the electorate for their discipline and resolve.
As late as last autumn, the certainty that this mechanism was working well had become a joke. The joke was Marlene.
We were enjoying a smug confidence that Arlene Foster and Martin McGuinness had virtually merged into a single entity. But the election of last year had shown a slide in the overall nationalist vote.
Nationalists, it seemed, were not as nationalistic as unionists were unionist.
And that suggested a possible trend by which our power-sharing, two-party rule model might ultimately disintegrate. Which would be fine if you were a unionist, or if you were out of a nationalist community but not personally all that fussed about community identity or a united Ireland.
From the perspective of Gerry Adams, it must have seemed as if the communal vote was being eroded at the edges. The people relied on to vote Sinn Fein were staying at home, or they were voting for the Greens. They were fretting not so much about a united Ireland but challenging canvassers on the doorstep about abortion or same-sex marriage.
In Ballymoney, a group of Catholics canvassed for the DUP as the party most likely to oppose abortion.
In South Belfast, nationalists swung from the SDLP and Sinn Fein to the Greens who were most likely to support abortion.
In short, Northern Ireland was starting to look like any other polity and voting on issues rather than on the constitution. But this was not symmetrical - it was more likely to happen in the nationalist community than in the unionist.
That, I suggest, is why Gerry Adams crashed the system.
Nationalist politics had to be resectarianised.
The next electoral showdown was brought forward over the RHI scandal and the question of Arlene Foster's position as First Minister.
The nationalist vote was rallied on the assertion that unionists were not treating nationalists as equals.
Nor, of course, were they. Successive DUP ministers had sneered at the idea of an Irish Language Act when they might instead have quietly relished the fact that a culture war was so much less bloody than what had preceded it.
The Assembly election in March brought a huge swing to Sinn Fein, probably supported by a gay vote.
Unionism got its vote out for the General Election this month and registered a huge advance, shaking off the fear that the two communities were drawing level.
By this Thursday, they should both be translating their successes into a willingness to agree the restoration of devolution. However, will they?
Each has actually thrived on deadlock.
Each may feel confidently that its electorate wants it to dig in.
Each may be tempted to prolong a stalemate that has proven so fruitful.
And each has a bigger game to play elsewhere while it waits for the next electoral test of its commitment to devolutions, the DUP at Westminster, Sinn Fein in the Dail.
Gerry Adams is going to demand seats there and speaking rights for his northern MPs. He might even, by Christmas, be leading the governing party that could open the door for them. That's where his focus is.
It appears that Stormont can wait.