The Labour Party has selected Senator Alan Kelly to contest the South constituency seat in next year’s European Parliament elections.
Mr Kelly defeated Arthur Spring by 276 votes to 144 in the ballot in Cork this evening.
A total of 420 candidates cast their votes out of a possible poll of 1,376.
Mr Kelly (33), of Portroe, Nenagh, Co Tipperary, was elected to the Seanad in 2007 on his first attempt, representing the constituency of Tipperary North.
He is the party’s tourism spokesman, Seanad spokesman on finance and a member of the Oireachtas Committee on European Scrutiny.
Mr Spring (31), from Tralee, Co Kerry, is a nephew of former Labour Party leader and former Tánaiste Dick Spring, for whom he worked as parliamentary assistant.
Labour Party leader Eamon Gilmore said it was "imperative" that the party unite behind the chosen candidate after today's contest, and to work to win the European Parliament seat for Labour.
"Our objective is to win, not only in the European elections, but in every electoral area in which we run candidates in the local elections next June," he said.
A series of disputes in the past week and the keen rivalry that has emerged between two candidates has led to heightened interest in what is usually a low-key event.
Mr Kelly expressed his disagreement with a decision by an appeal committee to allow late registration for 280 members, 238 of whom come from Mr Spring's stronghold of Kerry. Mr Spring expressed his disappointment that a postal ballot had not been allowed.