Sinn Fein President Gerry Adams will resign his seat in both the Northern Ireland Assembly and Westminster to stand for election in the Republic of Ireland.
The shock move would leave the West Belfast MP without any political office if he fails to hold the Sinn Fein seat in Co Louth, on the southern side of the Irish border.
The Republican leader will address supporters at a commemoration in the county where he will detail the reasons for taking what is arguably the biggest gamble of his political career.
Mr Adams will detail his plans in a speech to republicans at the rally in Edentubber, Co Louth.
The move comes as Northern Ireland faces Westminster cuts to the Assembly budget, but also at a time when the Republic faces a dire economic future.
Mr Adams is expected to tell supporters: "As the leader of Sinn Fein, in this time of crisis in our country, I am making a stand with this initiative - a stand for a better, fairer, united Ireland."