Taoiseach Simon Harris has said that "the Fine Gael family is in mourning" following the death of Roscommon councillor John Naughten.
Mr Naughten, a brother of former government minister Denis Naughten, was due to stand for Fine Gael in the upcoming general election.
He was selected to run in the Roscommon-Galway constituency at a party selection convention two weeks ago.
John Naughten had been a member of Roscommon County Council for over 20 years.
"John was a decent, gentle, personable and hard-working man. He had friends and close colleagues across the political spectrum. He was a caring father, brother, son and husband," Mr Harris said.
"I have been in close contact with John in recent months and weeks and his diligence as a public representative was easy for all to see. It was always in his blood, but John's political brain was quick-thinking and shrewd.
"John was a passionate farmer and a tireless advocate for the people of Roscommon. We have lost a talented politician, but much more tragically, a close and wonderful family have lost a loved husband and father.
"To John's wife Breda, to his daughters Emma, Leah and Orlaith, to his mother, Mary, as well as his siblings Marian, Aine, Denis, Seamus, Liam Óg, Joseph and Dermot, I am so sorry for your loss."
Minister for Justice Helen McEntee described John Naughten's death as utterly devastating for his family, his neighbours and his colleagues.
"John was a diligent, astute and very hardworking public representative, who would have had a very positive impact in Dáil Éireann. He was a team player who understood his community and wanted only the very best for it," the minister said.
She expressed her condolences to his wife and family.
Fine Gael's Frank Feighan has been a close colleague of his for two decades.
He said everyone is shocked by his death.
He described John Naughten as "a good friend, a great colleague and a good man".
