Labour Party TD Alan Kelly will this week announce his intention to run for the leadership of the party.
The nomination contest officially opened yesterday afternoon and will close in two weeks.
Mr Kelly secured a nomination from one of his parliamentary colleagues which means he can avoid seeking the support of Labour constituency councils.
The Tipperary TD was unable to contest the last leadership bid after failing to secure a parliamentary party nomination. The other potential leadership contenders, Ged Nash and Aodhan O Riordain, were silent on their intentions.
Mr Kelly's team say he has strong support around the country but he is concerned about winning votes in Dublin where there is a high concentration of Labour members.
The Labour Party Executive Board met in the Gresham Hotel in Dublin yesterday to agree on the rules for the contest.
Postal ballot papers will be sent to Labour members on March 15 and the closing date for returning votes will be midday on April 3. The party expects between 2,500 and 5,000 people to be eligible to vote. A voter must be a fully paid-up member for 21 days before polling day - meaning the last day they can sign up is March 13.
Labour Party leader Brendan Howlin announced last week that he intended to resign following the election.
He also said the party would not be entering into any government arrangement with the larger parties.