How the race is run
The Labour Party's 5,000 members will have a month to decide who to vote for to be their next party leader – and the next Tanaiste in the Coalition.
The new party leader will be elected by July 4, when the postal votes are counted. The Labour deputy leadership contest will be run parallel with the leadership race.
Leadership candidates will have to campaign for the next month and engage in at least five leadership debates attended by party members, with events expected to be held in Dublin, Cork and Galway.
About 40 per cent of the 5,000-strong party membership is based in Dublin, with substantial blocks also in Cork city and Kerry, Tipperary, Wexford, Kildare and Westmeath.
Willie Penrose's branch in Ballynacargy, Co Westmeath, has 150 members alone.
A contest for the leader's position was held in 2002 when Ruairi Quinn was replaced by Pat Rabbitte and 88 per cent of members voted on that occasion.
Eamon Gilmore took over in 2007 without a contest, but there was a competition for deputy leader, which was won by Joan Burton.
Labour's legal adviser, Richard Humphreys, a councillor in Dun Laoghaire-Rathdown, will be the returning officer.
Labour's Executive Board decides upon the election process.
Nominations will close at 12 noon on Tuesday. Candidates have to be proposed and seconded by TDs.
A postal vote will then take place over the following four weeks.
The counting of ballots will be on July 4 with a result expected to be declared that evening.