Senator David Norris has secured the backing of 17 TDs and Senators to contest the Presidential election.
Senators Mary Ann O'Brien and Eamonn Coghlan signed his nomination papers today to leave Mr Norris three signatures short of the 20 Oireachtas members he needs.
Senator O'Brien said she had made her decision after discussions with Mr Norris over recent days.
She said: "On hearing David's explanations to my concerns I now feel satisfied that I am in a position to sign Senator Norris's nomination papers.
"I do not believe it would be appropriate for me to block David's attempts to contest this election.
"The people of this country should be afforded the opportunity to pass their verdict on Senator Norris's candidature."
Last night, Mr Norris received the backing of John Halligan TD and Senator Mary Lousie O'Donnell.
So far the Oireachtas members nominating Mr Norris are: TDs Stephen Donnelly, Catherine Murphy, Maureen O'Sullivan, Mick Wallace, Joan Collins, Joe Higgins, Clare Daly, John Halligan and Richard Boyd Barrett, as well as senators Katherine Zappone, Mary Louise O’Donnell, Mary Ann O’Brien, John Crown, Fiach Mac Conghail, Seán Barrett and Eamonn Coghlan.
As a Senator, Mr Norris has also nominated himself.
TD Seamus Healy said this evening that he would be nominating or supporting any candidate.
Mr Healy said that he had hoped the Presidential election could be treated as an opportunity to challenge austerity and the EU/IMF deal, but that as no candidate was standing who espoused this position.
Senator Ronan Mullen confirmed this evening that he would not be nominating Mr Norris. His announcement was not unexpected.
That leaves just two members of the Oireachtas who have not declared their intentions - Independent TDs Shane Ross and Mattie McGrath.
Mr McGrath has said he will make a decision by Saturday on whether or not to nominate Senator Norris.
Mr McGrath said Mr Norris should be allowed to run for the presidency.
Mr McGrath said he would be meeting with his supporters tomorrow night to tell them that.
He said he wouldn't like to be the person to deny Mr Norris the chance to run and that he (Mr McGrath) "would facilitate the democratic process".
If Mr Norris were to get two more nominations, it is possible, though not certain, that Tipperary North TD Michael Lowry might be willing to give him the final nomination.
Senator Fergal Quinn said he has nominated Seán Gallagher for the presidency and does not intend switching his nomination to anyone else.
Independent TD Thomas Pringle informed Mr Norris that he would not be in a position to sign his nomination papers. He made his decision after meeting Senator Norris this morning.
The Taoiseach has said that Fine Gael councillors will be abstaining in council votes on the candidacy of Mr Norris and Dana.
Kilkenny County Council announced this evening that it would be holding a special meeting at 8.30am next Wednesday morning to vote on Presidential nominations.
A Garda escort will be on standby to bring any completed nomination form to Dublin before the midday deadline.
The chairperson of the council, Paul Cuddihy said this evening the meeting had to be moved from Monday to Wednesday because of a requirement in their standing orders that they give three full working days notice of meetings.
Mr Cuddihy added that because the nomination of Mr Norris was the first one received by the council that will be the first one discussed and voted on at the meeting.
If the council does not support Mr Norris, a discussion and vote will follow on Ms Scallon's nomination.
Mr Norris received the backing of Fingal County Council earlier this week.
Separately, South Dublin County Council is due to meet on Monday to decide whether it will nominate the Senator.
Dublin City Council is to hold a special meeting next Tuesday to consider nominating Senator David Norris for the Presidential election.
Maria Metcalfe (Ind), Bríd Smith (PBPA), Pat Dunne (PBPA) Mannix Flynn (Ind) and Cieran Perry (Ind) were the five signatures required to request the meeting.
The request was agreed by Lord Mayor Andrew Montague (Lab) this evening.
Ms Scallon is also continuing efforts to get nominations from either four local authorities or 20 Oireachtas members.
Roscommon and Carlow councils are also due to meet on Monday. Waterford City Council is to meet next Tuesday. These three councils will consider both Mr Norris and Ms Scallon.
There are indications Donegal County Council may back Dana after it emerged Fianna Fáil councillors have secured a special meeting of the council on Tuesday.
Longford County Council will vote on Tuesday afternoon on whether to nominate Ms Scallon. The motion is being proposed by Fianna Fáil councillors.
Fine Gael's Gay Mitchell, Labour's Michael D Higgins, Sinn Féin's Martin McGuinness and Independent candidates Mary Davis and Seán Gallagher have already secured nominations to contest the election, which takes place on 27 October.