The Tánaiste (Irish deputy prime minister) Frances Fitzgerald has given her backing to Leo Varadkar to succeed Enda Kenny as Fine Gael leader and taoiseach (Irish prime minister).
Mr Varadkar, who is the minster for social protection, officially launched his campaign in Dublin on Saturday.
He currently has the support of 45 Fine Gael parliamentary members.
Simon Coveney, the current housing minister, handed in his nomination papers on Thursday.
Mr Varadkar told supporters during his campaign launch speech that he wanted to see a truly united Ireland for all members.
“If elected as leader of this great party and taoiseach, I will work to honour the public trust and ensure we govern with integrity in all things,” he said.
“Fine Gael must be a party that can win support from all parts of the country and from people of all backgrounds.”
The Dublin West TD now has the support of 45 members of the parliamentary party which equates to 40% in the overall contest.
Mr Coveney has the pledged support of 20 members of the parliamentary party.
On Saturday morning, Mr Coveney cancelled a planned media event at his constituency office in County Cork in relation to his leadership bid.
This had led to speculation that he may have been considering pulling out of the race but on Saturday evening he told supporters at a rally in Cork city centre that he was going to finish what he had started.
Arriving for the rally, Mr Coveney said: “No second thoughts – that’s not my style.”
Mr Varadkar and Mr Coveney are the only two candidates in the running to take over as leader of the party.
On Sunday, the two leadership contenders are involved in their first full day of campaigning since the close of nominations on Saturday evening.
Fine Gael will choose its leader through an electoral college system in which weighed votes are given to different branches of the party.
- 65% is allocated to members of the parliamentary party
- 25% is given to unelected party members
- 10% is allocated to county councillors
While Fine Gael members have the power to pick the new leader of their party, Dáil TDs (Irish MPs) must then vote on whether or not they become taoiseach.
Mr Kenny stood down as the party’s leader earlier this week, but will stay on as prime minister until his successor is chosen.
Over the last year, Mr Kenny led a minority government, which was propped up by an alliance of independent TDs and required the support of the opposition party – Fianna Fáil – to pass its budgets.
Mr Kenny leaves the Fine Gael leadership as the party’s most successful taoiseach.
In a statement announcing his retirement, he said it had been a “huge honour and privilege” to lead the party over the course of 15 years.