Minister for Further and Higher Education Simon Harris has confirmed his intention to run for leadership of Fine Gael, having already received support from nearly half of the parliamentary party.
Nominations for candidates opened at 10am.
Speaking to RTÉ's Six One News, Simon Harris said he wants to be the next leader of Fine Gael and that he was "ready to step up".
He also said he had been "overwhelmed and extremely grateful" for the support he has received from party colleagues.
"I want to thank everybody for their support and their trust. It means so much to me and I will work night and day. I will give this my absolute all to repay that trust."
He added that he wants to bring "energy and an enthusiasm" to the leadership of the party, as well as his "practical life experience".
"I want to work with colleagues, I want to listen, I want to really reconnect with our party right across the country. I want to get back to core principles."
Watch: Simon Harris announces intention to run for party leadership
In a statement this evening, Mr Harris thanked Leo Varadkar for his leadership of the Fine Gael party over the past seven years, and for his leadership of the country, saying he had "steered our party and our country through very challenging times including Brexit, the Covid-19 pandemic, and the recent cost-of-living crisis."
Ministers Helen McEntee and Heather Humphreys have ruled themselves out of the running and said they would support Simon Harris.
Minister for Public Expenditure Paschal Donohoe has also said he will not run, while the party's deputy leader Simon Coveney ruled himself out yesterday.
Some in the party, like TD Richard Bruton and Senator Seán Kyne, have expressed the view that they would like to see an election, however that would require a second candidate.
Outgoing Fine Gael leader Leo Varadkar said this morning that while a contest can be beneficial, it is not essential.
Speaking in Brussels, Mr Varadkar also said that he would not be endorsing a particular candidate to succeed him.
"It's a very long-standing tradition in Fine Gael, and a very good one, that outgoing or former party leaders don't endorse a particular candidate," he said.
Minister of State Neale Richmond, Senators Barry Ward and Tim Lombard, as well as MEPs Frances Fitzgerald and Maria Walsh were among the first to declare their support this morning.
Speaking on RTÉ's Morning Ireland, Mr Richmond said that he will "absolutely" be backing Mr Harris and will not consider voting for any other candidate.
Ministers of State Jennifer Carroll MacNeill and Hildegarde Naughton, along with Senator Seán Kyne, have also said they would support Mr Harris.
Senator Kyne said the firm view of the Fine Gael party executive council is that there should be an election, and he will act to facilitate that.
Senator Regina Doherty and Deputy Fergus O'Dowd also want an election.
The Fine Gael Executive Council decided last night that nominations to become the next party leader would open at 10am today and close on Monday at 1pm.
It is possible that there will only be one candidate should Mr Harris be viewed by rivals as having built-up an unassailable lead.
Fine Gael parliamentary party Chair Alan Dillon said that: "One would expect there will be a contest" for the leadership.
Speaking on RTÉ's Morning Ireland, he added: "I think everyone would welcome a contest. Having a contest will allow those candidates to engage with the membership all across the country."
Asked who he might support, Mr Dillon said he felt it would be "unfair" to express his personal preference given his position as chair, and his role in ensuring that any contest is conducted in a "dignified manner."
The Mayo TD expressed the view that Fine Gael could win a "historic" fourth successive term in Government in the next general election.
His party colleague, Deputy Colm Brophy, told RTÉ's Today with Claire Byrne that he wants Mr Harris to be the next leader as he is "absolutely" the right person to "re-energise" Fine Gael and bring success in elections.
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Candidates must be nominated by at least six members of the parliamentary party, which is comprised of TDs, senators and MEPs.
The executive council, which decides on the rules of the leadership election campaign, says before any votes are cast, three regional meetings will take place with candidates on Tuesday, Wednesday and Thursday of next week.
Votes will be weighted in accordance with the Fine Gael electoral college rules: the 54 members of the parliamentary party account for 65% of the total vote; 20,000 party members accounting for 25%; and 249 local representatives account for the remaining 10% of the vote.
Voting for almost 20,000 eligible party members will take place nationwide at more than 20 polling stations from 2-4 April.
Party members must be affiliated for at least two years to be eligible to vote.
All votes will be brought to a national count centre on 5 April, where they will be verified and then counted.
The result will be officially announced at the count centre on 5 April.
Additional reporting Paul Cunningham
