Britain's Northern Ireland minister, James Brokenshire, will be obliged to dissolve the assembly if the main nationalist party Sinn Fein - which, tellingly has already begun picking election candidates - fails to name a replacement for him by a 1700 GMT deadline on Monday.
Sinn Fein - once the political arm of the IRA - has refused to fill its senior spot in the coalition after Martin McGuinness resigned as deputy first minister on January 9 effectively toppling the devolved government.
His resignation automatically removed the leader of the pro-British Democratic Ulster Party (DUP), as the First Minister cannot hold the position without a co-equal Deputy First Minister.
Ostensibly the move was triggered by First Minister Arlene Foster's handling of a controversial green-energy scheme as deputy first minister, but fault lines - some ancient and others much newer - are nearing the political surface.
"Sinn Fein will not be nominating for the position of deputy First Minister and the agreements mean that the people must now have their say," Sinn Fein minister Michelle O'Neill said in a statement on Sunday.
McGuinness said he will announce shortly whether he will lead Sinn Fein into the election, suggesting the vote will be followed by renegotiations of the terms of the power-sharing government.
Old wine in new bottles
The over-budget green energy scheme is one of several issues on which the two parties have clashed in recent months.
The key fault line appears to be over Brexit, with the DUP wanting the UK to leave the EU and Sinn Fein taking the opposite position.
Sinn Fein also wants to legalize same-sex marriage in Northern Ireland, but the DUP does not, while the latter has also withdrawn funding for an Irish language bursary scheme, angering nationalist parties.
Added to this there are also disagreements over how new agencies set up to investigate killings from the Troubles (the period from 1969 when the province erupted in violence until the 1998 agreement) should operate.
So long Good Friday?
The basic principle of power-sharing between British Protestants and Irish Catholics underpins the 1998 peace accord - the Good Friday agreement - and has been buttressed in practise by a nine year-old coalition led jointly by Sinn Fein and the major Protestant-backed DUP.
The agreement ended three decades of violence between mainly Catholic Irish nationalists seeking a united Ireland and Protestant pro-British unionists wanting to remain part of the UK. Some 3,600 people were killed in those years.
The EU question
Northern Ireland is perhaps the UK's most exposed to post-Brexit fallout because of the prospect of checkpoints being reinstalled on its land border with the Irish Republic, an EU member.
New power-sharing talks may begin as British Prime Minister Theresa May begins exit talks with the EU, after Article 50 is triggered at the end of March.
On Monday afternoon, May made a last-ditch attempt to get Northern Irish leaders to solve the political impasse.
"Political stability will give the province a stronger voice in Britain's Brexit preparation," her spokeswoman said.
"She (May) spoke to both Arlene Foster and Martin McGuinness, wanting to encourage them to take what time is left today to try and find a resolution," the spokeswoman said.
"Having clear political stability and ministers in place in Northern Ireland provides a greater opportunity for them to have
their voice heard," she added.
A failure to form a new ruling executive after the elections also risks the suspension of the province's political institutions and the return of its 1.8 million people to direct rule from London.
The last time devolution was suspended, there was direct rule from Westminster - ministers from the British government took over the province's departments.
Nationalists are calling for a form of "joint authority, where the British and Irish governments share responsibility for running Northern Ireland.
Brokenshire said he is not contemplating any alternatives to devolved government and refused to be drawn on the possibility of Northern Ireland being run on the basis of a "joint authority" with Dublin.
It is just eight months since the last assembly election, when in May 2016 the DUP and Sinn Fein were well ahead of their rivals.
jbh/rt (AP, Reuters)