True to form, Belfast is once more mired in a January crisis. On Monday, Martin McGuinness, from the Irish republican party Sinn Fein, resigned as deputy first minister, almost certainly triggering fresh elections. Many fear that Northern Ireland will have no government in place at arguably the most important moment in its modern history: Brexit.

This year's crisis could prove to be the most serious since the Good Friday peace agreement was signed in 1998. Unusually the current difficulties have nothing to do with flags, parades or the legacy of the 30-year-long Troubles that cost more than 3,000 lives. At the core are fundamental questions about whether nationalists and unionists can work together in a devolved government.

The immediate catalyst for McGuinness' resignation was a botched energy scheme that could cost Northern Irish taxpayers 490 million pounds (562 million euros). The renewable heating incentive (RHI) was created in 2012 at the approval of Arlene Foster, then enterprise minister and now Northern Ireland's first minister and leader of the Democratic Unionist Party (DUP).

Foster refused repeated calls to step aside while the scheme was investigated. So McGuinness resigned.

On Monday, a visibly-ill deputy first minister issued a strongly-worded letter excoriating the DUP, his coalition partners for almost a decade, for failing to uphold the spirit of bi-partisan politics that Northern Ireland's institutions are ostensibly founded upon. A decision by the DUP, announced on December 23, to withdraw a 50,000-pound bursary scheme for the Irish language was seen by many republicans as symptomatic of an absence of good faith.

The Northern Irish assembly was elected last May but a fresh vote will be called next week if Sinn Féin does not nominate a replacement as deputy first minister. McGuinness has said that the party will not do so.

Brexit uncertainty

Northern Ireland's political instability could have a significant bearing on Brexit, too. When Britain triggers Article 50 in March, it is very likely that the one part of the UK that shares a land border with the EU will have no government.

"A significant part of this island will have nobody representing it in the Brexit negotiations. At a crucial moment for Northern Ireland we won't be represented," says Dr Johnny Byrne, lecturer in politics at the University of Ulster.

"This is the most significant moment since the Good Friday Agreement. This goes well beyond cultural and symbolic issues, this goes to the very heart of sharing power and making collective decisions," he told DW.

Northern Ireland voted to remain in the European Union, and many fear that the UK's exit could pose significant economic and political problems, especially around the circuitous 300-mile border long border with the Irish Republic. Irish EU Commissioner Phil Hogan has called for the whole island of Ireland to be treated as a single unit by the European Union. This would ensure the freedom of goods and people on the island and avoid a border for customs or immigration.

But Foster - whose party backed Leave - has rejected calls for an all-Ireland forum on Brexit and played down fears of post-Brexit problems. Critics have accused the DUP leader of failing to appreciate the potential risks faced by Northern Ireland.

Political intransigence

Stephen Farry, a member of the Northern Irish assembly for the cross-community Alliance Party, said that Northern Ireland needed "a proper plan to argue for special arrangements being put in place for us." Any prospect of such an agreed position on Brexit will likely evaporate if, as expected, the political institutions in Belfast collapse in the coming days.

The British government has said that it will try to facilitate an agreement between the DUP and Sinn Fein in the coming days but few believe such a compromise is possible. Many Irish republican voters have become increasingly frustrated by what they see as political intransigence from the DUP, the largest party in the devolved assembly.

"The republican leadership had been hearing its grassroots question the viability, credibility and work-ability of the Stormont institutions and openly question the supposed partnership with the DUP," said veteran Northern Irish journalist Barney Rowan.

Years in the wilderness

McGuinness' reaction this week was, in part, a reaction to growing grassroots republican anger. "In their thinking, 10 years of government with the DUP have not worked and the republican mood suggests there won't be 10 more years, unless there is a dramatic, certain and very different relationship going forward," Rowan told DW.

The rift between the coalition partners seems so deep that even fresh elections are unlikely to solve the problem. With the number of seats in the assembly decreasing from 108 to 90, (a move that has been on the agenda for some time in an effort to reduce the strain on public finances - the ed.) and smaller parties hoping to take advantage of widespread discontent with the status quo in Belfast, the election campaign could be a bitter one with little sign of how a government can be formed at the end of it.

"We are into a long negotiating process here. This is about the Good Friday Agreement, this is about shared collective government The DUP didn't negotiate the Good Friday Agreement. They have no psychological attachment to the Good Friday Agreement," said Byrne.

"We could be a year or two without a government here."