John O'Dowd replacing McGuinness as deputy first minister
Stormont Education Minister John O'Dowd has been designated as temporary deputy first minister in the assembly.
It follows confirmation that Martin McGuinness will be Sinn Fein's candidate in next month's Irish presidential election
Mr O'Dowd's nomination does not require cross-party support, but is a matter solely from Sinn Fein.
He will assume the responsibilities of the deputy first minister from midnight.
Mr O'Dowd said he did not foresee any problems in establishing a working relationship with First Minister Peter Robinson of the DUP.
"I intend to work closely with Peter Robinson in the weeks ahead for the betterment of our society," Mr O'Dowd said.
"What we (Sinn Fein) will be doing is ensuring the executive and assembly run smoothly."
Mr McGuinness is stepping down as deputy first minister during the campaign to succeed Belfast-born Mary McAleese as Irish president.
He said he had confidence in Mr O'Dowd's leadership qualities.
"The good work that has been done here over the last number of years will continue," he said.
Earlier, he said, if elected, he would only take "an average wage" and that the rest of his salary would go back to the public purse.
He added: "A number of people in the north who lost loved ones as a result of the actions of the IRA have actually come to me and pledged their support in this campaign.
"That gives me tremendous encouragement because I think they see me as someone who has been at the heart of the Good Friday Agreement, the negotiations that brought about the St Andrews Agreement, the Hillsborough Agreement, and the building of very important relationships with our unionist brothers and sisters."
Mr McGuinness said he expected his past as an IRA commander to be brought up during the course of the election campaign.
"I have promoted peace everywhere that I have gone but I know there will be a very strong temptation for people to drag us back to the past.
"God knows there are enough of them trying to do so, in a violent sense, at the moment," he said.
"But I am of the here and now and I am someone who is very focused on the future."
Ulster Unionist party leader Tom Elliott said it was a matter for people in the Irish Republic who they elected, but that it would help if Mr McGuinness disclosed some of his activities with the IRA.
"I think it would be extremely useful if he were to sit down and talk of his overall involvement," he said.
"Of how he was a commander in the IRA, what those actions enabled him to do, what some of the actions were that he did take and an acceptance that their campaign was wrong."
DUP MP Ian Paisley said: "If our politicians who are problem politicians decide to export themselves to the south of Ireland then that's probably not a bad thing.
"It clears the way for new blood to enter real politics in Northern Ireland.
"It's been a lot of the baggage that people like Martin McGuinness have carried with them to the political scene that has caused difficulties."
Mr McGuinness has secured the necessary support of independent members of the Irish parliament for his nomination.
They are Finian McGrath, Luke Flanagan, Michael Healy-Rae and Tom Fleming.
"Our history is steeped with former gunmen turned politicians, examples are Michael Collins, Sean Lemass and Eamon De Valera," Mr McGrath said.
"I have always supported the peace process and the democratic peaceful politics on this island."
Fine Gael's Gay Mitchell, Special Olympics boss Mary Davis, businessman Sean Gallagher and Labour's Michael D Higgins of Labour, have already put their names forward.