Northern Ireland's "Troubles," the ethno-sectarian conflict between republicans and unionists that claimed more than 3,000 lives, officially ended with 1998's Good Friday accords. Now, 18 years after this agreement mostly ended three decades of violence between Catholics who wanted to join the Republic of Ireland, and Protestants who wanted to stay British, Northern Ireland's power-sharing agreement hangs in the balance.

After several weeks of political turmoil, First Minister Peter Robinson has stepped aside, accusing republicans in the assembly of pushing "devolution to the brink," referring to the UK's process of devolution handing broad authority to the parliaments of Scotland, Wales and Northern Ireland. Other ministers from Robinson's Democratic Unionist Party (DUP) are also set to resign.

The crisis was sparked by the murder of ex-IRA hit man Kevin McGuigan last month. A police assessment suggested that members of the Provisional IRA, the main republican paramilitary group, may have been involved in the killing. A central reason that unionist politicians in the Democratic Unionist Party (DUP) agreed to share power with the nationalist party Sinn Fein in 2007 was the IRA statement of 2005, which suggested that the latter was dissolving as a military force.

It is no secret that some former IRA members rejected the 1998 Good Friday agreement and remained active in "dissident" military groups. Some use variations on the IRA name, but most are small. But the continued existence of the main IRA group raises questions about Sinn Fein and the mainstream republican movement. The political row escalated on Wednesday, when detectives arrested a senior member of Sinn Fein as part of the murder inquiry. The party's chairman for the north of Northern Ireland, Bobby Storey, was released a day later and plans to sue for wrongful arrest.

'Not on a war footing'

Police are clear that there is no evidence that the McGuigan murder was sanctioned by anyone senior in the republican movement. "They are not on a war footing, they are not involved in paramilitary activity in the sense that they were during part of the conflict," says George Hamilton, chief constable of Northern Ireland. "Nevertheless we assess that, in common with the majority of Northern Ireland paramilitary groups from the period of the conflict, some of the PIRA [Provisional IRA] structure from the 1990s remains broadly in place, although its purpose has radically changed since this period."

As a result of the apparent IRA links to the murder, the DUP issued an ultimatum, saying that its ministers would resign if the assembly was not adjourned. The other parties – Sinn Fein, the Ulster Unionists and the Social Democratic and Labour Party (SDLP) – all voted against the adjournment motion on Thursday.

With the exception of Arlene Foster, the DUP's ministers have all signed their letters of resignation. "Robinson has left the power sharing government in zombie form by keeping one single minister inside. It buys the talks process about six weeks breathing space," says Henry McDonald, Ireland correspondent for the Guardian newspaper. "After that, if there is no breakthrough there will be no devolution. Then the project will collapse."

Prime Minister David Cameron will hold talks with political leaders while he considers whether to take the significant step of suspending the assembly. Downing Street said the Prime Minister was "gravely concerned."

"Power-sharing now hangs by a thread," says Guy Lodge, associate director at the Institute for Public Policy Research. "The best hope for a deal rests on the fact that a vast majority of people in both communities are opposed to a return to violence. And all parties ultimately prefer the devolution to a return to direct rule from London. Recent history suggests that talks between the two sides can break the deadlock - though this time trust is at an all-time low creating a very uncertain future."

Politics too defined by constitutional question?

There is a widespread sense of disillusionment with the political process in Northern Ireland. In all but one constituency in the 2015 general election, those who did not vote outnumbered those who voted for the winning candidate.

"The politicians at Stormont, in nearly every party, are performing a play that lost its audience long ago. It is hard to find anyone in Belfast who really cares about them, one way or the other," says Gareth Russell, Belfast-based author. "I would like to see a new set of political parties that campaign on issues and find a place on the political spectrum - conservative, socialist, liberal - rather than the current parties, many of whom rely on votes based purely on their constitutional position. Like many people, I would like to stop regarding the executive as a distasteful political sideshow."

The devolved government was at the center of the peace agreement in Northern Ireland. Its absolute collapse would be unprecedented, and risks reigniting bitter community divisions. "I don't think we will see a return to violence - Northern Ireland has come a long way in the last 18 years," says Belfast resident and lawyer Conor O'Brien. "Most communities are opposed to more violence, even those who support the republican cause. But of course we are always concerned to an extent about a return to the bad old days of neighbors turning on neighbors. We have a fragile peace so this is a very frightening thing."

Others see the political turmoil as part of the problem. "I'm not worried at all about the resurgence of community tensions," says Russell."They have been both exaggerated and inflamed by the largest parties in the Stormont executive, who rely on those concerns to generate the largest share of their votes. Life in Northern Ireland has moved on, it is a great place to live, but the largest parties - including Peter Robinson's - cannot make that adjustment. They look back because they do not have the intellectual talent to look forward. It is extremely frustrating. They are the authors of, not the solutions to, many of our problems."