The contenders for the Green Party leadership, Minister for the Environment John Gormley and former Dublin MEP Patricia McKenna, have each been nominated for the position by 50 party members, as required under the rules for the contest, a party spokesman said last night.
While nominations remain open until Friday, party sources said it was unlikely there would be any other candidates.
Voting is by postal ballot, with ballot papers being sent out next Monday.
Polling will close on Tuesday, July 17th, and the new leader is expected to be announced the next day.
Mr Gormley was a key figure in support of the coalition arrangement with Fianna Fáil, whereas Ms McKenna opposed the deal.
However, Ms McKenna said in her e-mail message seeking nominations: "This will not be a campaign to rehash the decision taken in the Mansion House to go into government with Fianna Fáil and the PDs.
"Regardless of whether one supported the proposal or opposed it, we have to work with the decision, and ensure that our TDs get all the backing and support they need. And I have a feeling they will very much need it."
Sources close to Mr Gormley said last night: "John was centrally-involved in the negotiations to go into government, a decision which had the support of the entire parliamentary party and 87 per cent of the members at the Mansion House special convention, and obviously a leader who didn't support this deal would place the party in a difficult position."
Ms McKenna told The Irish Times that only a leader who was outside the parliamentary party, such as herself, could provide the "impartiality and independence" that were required at this time.
Meanwhile, supporters of Mr Gormley said: "He will ensure there is a proper link for councillors and party members to the Green Party members in Government. He has also promised an enhanced role for the national council, the party's main policy-making body."
Ms McKenna said: "It is vital that people stay within the party and continue to contribute, to ensure that we maintain the ideals and principles on which we were founded."
Mr Gormley's supporters said: "He is someone who can take difficult decisions and also face the consequences, and our leader will have to be someone like that."
The contest arose when Trevor Sargent announced at the Mansion House convention on June 13th that he was stepping down, in line with a pledge that he would not remain as leader if the party entered government with Fianna Fáil.