At 27, Mr Butler is the youngest serious contender for a seat in this constituency. He will have his work cut out, however, if he is to get more first-preference votes than Ahern, which he will need to have any chance of success.
From Ballycallan, Co Kilkenny, he joined the Labour Party in 1990 and is a former member of the party's general council. A sales executive with Duggan Steel in Kilkenny, he was educated in St Kieran's College, Kilkenny, and Carlow Institute of Technology. He holds an honours degree in services marketing.
He caused a major shock by winning the Labour nomination over the Louth TD, Mr Michael Bell, by 67 votes to 31. Having successfully seen off a challenge for the candidacy by Mr Peter Cassells, the general secretary of the ICTU, Mr Bell had been confidently expected to get the nod.
Mr Butler, however, canvassed almost 100 delegates in the run-up to last September's convention, taking Mr Bell and the party hierarchy by surprise.