Fine Gael presidential candidate Mairead McGuinness has announced that she is withdrawing from the race.
In a statement released this afternoon, Ms McGuinness said the decision was not taken lightly, and followed a stay in hospital last week.
"My priority now is my health. Given that the election is in a short couple of months, I do not believe that I have the strength to give the campaign my all," she said.
In her statement, the former MEP and EU Commissioner explained: "I am taking this decision on medical advice and while it is extremely difficult, it is the right decision for me and my family.
"I appreciate that this will come as a shock and disappointment to party members and colleagues in Fine Gael, but our political family is strong."
Ms McGuinness said she had spoken to Tánaiste and Fine Gael leader Simon Harris to thank him for his support and understanding.
"I also want to thank all of those people who have done so much to support me, now and in the past.
"My focus now is my health and my family, and I ask for privacy in the time ahead," added Ms McGuinness.
Mr Harris said Ms McGuinness has "made an incredible contribution to public life in Ireland and in Europe".
'Great sense of shock in Fine Gael' on McGuinness withdrawal - Harris
In a statement, he said: "It was our clear view in Fine Gael and the view of many people across Ireland that Mairead would make an excellent president of Ireland.
"Mairead's health will not now allow this. This has come as an awful shock to us all. Mairead is a valued member of our Fine Gael family. It is absolutely essential that she now prioritises her health and I know I speak for everyone when I wish her all the very best on that journey," said Mr Harris.
He said there is a great sense of shock within Fine Gael.
"I know how hard she had been working to prepare for the presidential election," Mr Harris said, "but her health has to come first and it is absolutely crystal clear that on the basis of health advice that she is making the right decision".
Fine Gael to consider next steps in coming days
Minister for Agriculture, Food, Fisheries and the Marine Martin Heydon is Fine Gael's Director of Elections for the upcoming presidential election.
In a statement, Mr Heydon said: "The Fine Gael Executive Council will meet in the coming days to discuss the next steps, but for now, I, along with Mairead's many friends and colleagues within the party, send their very best wishes to her and her family."
Independent TD Catherine Connolly, who launched her bid for the Áras last month, said Ms McGuinness' decision came "as a shock".
"Without a doubt this decision could not have been an easy one for her to make. I would like to extend my best wishes to to Mairead and her family at this time, and all the best for the future."
Read more: Who are the potential runners and riders in the race for the Áras?
Ms Connolly has been steadily garnering support from left-leaning parties and TDs, receiving the backing of the Social Democrats, People Before Profit, the Labour Party and a number of independents.
Fianna Fáil has not run a presidential candidate since 1997, when its candidate Mary McAleese topped the poll, and the party is still undecided whether to enter this year's contest.
Mary Lou McDonald has repeatedly said that Sinn Féin is considering its options when it comes to the election and that an internal process is under way, with a decision to be arrived at in a few weeks.
RTÉ's Juliette Gash reports on Mairead McGuinness withdrawing from presidential race
