UPDATE 5.10pm: Nominations have closed for the Fine Gael leadership election.
The Candidates for party leader are Simon Coveney and Leo Varadkar.
Gerry O'Connell, Chairman of the Executive Council, has been appointed National Returning Officer for the Leadership Election.
Mr O'Connell said: "Nominations have now closed for the Fine Gael Leadership Election 2017. Next week, both leadership candidates will take part in four regional hustings, ensuring all members of the wider Fine Gael membership have an opportunity to engage in the process of electing the Party's new leader.
"This is the first time since the foundation of the State where a party has engaged on this scale and in such a transparent way in selecting its leader, giving all members a choice in who their next party leader will be.
"Since this process began earlier this week, it has engaged the public and energised the party, and will continue to do so over the coming days, weeks and months ahead," Mr O'Connell said.
Voting for almost 21,000 eligible party members will take place nationwide at 26 polling stations on Monday 29th May, Tuesday 30th May, Wednesday 31st May and Thursday 1st June.
Party members must be affiliated for at least two years to be eligible to vote.
The Parliamentary Party will meet and vote in Dublin on Friday, June 2 when all votes will be brought to a National Count Centre in Dublin to be verified and counted under the supervision of the National Returning Officer, Gerry O'Connell.
Votes will be weighted in accordance with the Fine Gael electoral college rules below:
UPDATE 4.10pm: Housing Minister Simon Coveney has decided to defy calls to withdraw from the Fine Gael leadership race, writes Daniel McConnell of the Irish Examiner.
Several sources within the Coveney camp had indicated he was considering his options earlier in the day and he had pulled out of a press event this afternoon.
But his campaign spokeswoman Caitriona Fitzpatrick has insisted he is not pulling out of the race and tonight's planned rally will proceed.
Really looking forward to a big FG rally tonight in Cork City!!— Simon Coveney (@simoncoveney) May 20, 2017
The Coveney camp have hit out at earlier suggestions Mr Coveney was coming under pressure to withdraw.
Mr Coveney's decision to continue comes despite 45 members of the 73 member Fine Gael parliamentary party backing his main rival Leo Varadkar.
UPDATE 2pm: Housing Minister Simon Coveney looks set to withdraw from the race to succeed Enda Kenny as Taoiseach just 72 hours into the campaign, writes Daniel McConnell and Fiachra O Cionnaith
He has cancelled a press event due to be held in Cork this evening, sources have told the Irish Examiner.
Should he do so, it would clear the way for Social Protection Minister Leo Varadkar to become Ireland’s first openly gay Taoiseach.
Leading members of Mr Coveney’s campaign are calling on him to withdraw from the Fine Gael leadership race as early as tonight, as they realise it cannot be won.
On foot of the decision of Tanaiste Frances Fitzgerald to support Mr Varadkar and a number of other key declarations, it is now virtually impossible for Mr Coveney to overtake his rival.
Mr Varadkar’s ‘Shock and Awe’ campaign has successfully captured the necessary momentum in the opening days of the campaign, which Mr Coveney’s team has found impossible to combat.
But party sources have today told the Irish Examiner that they feel Mr Coveney should withdraw from the race with immediate effect as they feel there is no way back for him.
Mr Coveney was due to hold a major rally in Cork this evening but the manner of his campaign has forced him to cancel the event in the past few minutes.
Mr Coveney is presently consulting with Fine Gael supporters ahead of expected announcement later this evening.
Update 12.45: Tánaiste Frances Fitzgerald has backed Leo Varadkar in the Fine Gael leadership race, at his campaign launch this afternoon.
She said: "(Leo) is committed, intelligent and determined. He is a deep analytical thinker with a diligence to turn his ideas into reality.
"Leo is the leader to renew and recommunicate Fine Gael values...let’s make these two weeks count and win in a decisive, generous way."
Leo Varadkar now has the support of 45 of the 73 members of the Fine Gael Parliamentary Party in the race to be the next leader.
Frances Fitzgerald’s support is in addition to that of junior ministers Michael Ring and Catherine Byrne and Senator Joe O’Reilly, who all also announced for him today.
He now has a virtually unassailable lead as Simon Coveney would require the support of around three quarters of Councillors and the wider Fine Gael membership.
Update 12 noon: Minister of State for Regional Economic Development Michael Ring and Senator Joe O’Reilly have announced their support for Leo Varadkar in the Fine Gael leadership race.
Varadkar is due to formally launch his campaign shortly, but has already secured a strong lead with 44 supporters in the 73-strong parliamentary party, to Coveney’s 19.
Party heavy-hitter and Tánaiste Frances Fitzgerald and Minister of State Catherine Byrne are widely expected to declare for My Varadkar at his launch in Dublin in the next hour or so.
With just hours to go before the nomination deadline, the Fine Gael leadership race is hotting up.
Leo Varadkar will officially unveil his campaign at lunchtime, with several members of cabinet expected to make an appearance at the launch.
Nominations officially close at 5pm today.
So far Government Chief Whip Regina Doherty, Ministers Paschal Donohoe, Charlie Flanagan and Helen McEntee have all declared their support for the Social Protection Minister.
Clare TD and Junior Minister Pat Breen is the latest to join the Varadkar camp, announcing it this morning. He said of Varadkar: "He’s the best qualified - he’s capable, energetic and has energy. Above all, he has vision, and that’s very important if you want to be a leader."
Meanwhile, Simon Coveney’s campaign team have urged grassroots Fine Gael members to “turn” national politicians supporting Leo Varadkar, after two Clare TDs controversially backed his rival just hours after the Housing Minister visited their constituency.
As reported in the Irish Examiner, Coveney team members made the claim as they insisted the race to replace Enda Kenny is not over and that they were always expecting to focus on councillor and grassroots support to gain power.
In a deeply controversial move last night, junior minister for employment Pat Breen and TD Joe Carey confirmed in separate statements they will back Mr Varadkar as they believe he is best suited to lead Fine Gael and the country.
While both TDs said the decisions had been made a number of weeks ago, they were publicly revealed just hours after Mr Coveney spent the day in Clare discussing housing policy and attending the Clare Fine Gael branch agm — with Mr Breen saying the delay was “out of respect” for the housing minister.
Despite Mr Coveney receiving the backing of ex-ceann comhairle Sean Barrett, Galway West TD Hildegarde Naughton and Louth TD Peter Fitzpatrick yesterday, the additions of the two Clare TDs and a host of ministers and backbenchers for Mr Varadkar means there is a 40-20 parliamentary party gap between the rivals.
And with just 13 crucial votes among TDs, MEPs and senators still up for grabs, Mr Coveney’s team have now turned their attention to councils and grassroots members in a bid to rescue their faltering campaign.
Who elects the next leader of Fine Gael?