Dun Laoghaire local Cormac Devlin has been selected by Fianna Fail to run in the hotly-contested constituency.
Devlin narrowly beat former minister and now councillor Mary Hanafin by just four points, but only after he benefited from transfers from Kate Feeney.
Ms Hanafin was ahead of Mr Devlin after the first count at the convention in Killiney Castle.
But after Ms Feeney's transfers were distributed, Mr Devlin was announced the winner by 68 votes to 64.
It marked the end of a tense race for the single slot on the ticket among three high-profile candidates.
Tensions among the trio further rose last week when Devlin - tipped to get the nod at the selection convention - warned party bosses that he would consider legal action if a diktat was issued from headquarters instructing delegates to select a female candidate - a practice that has come to be described as "gendermandering".
Speculation had mounted in recent weeks that Dun Laoghaire would receive a gender quota diktat from the party's national constituency commission following on similar instructions given to Dublin Central and Dublin South Central.
Fianna Fail have yet to hit the 30pc gender quota target required to avoid financial penalties.
However, no such ruling was applied to the ever-controversial constituency.
Around 170 party members arrived at the Fitzpatrick Castle Hotel yesterday for the proceedings, which were chaired by Senator Thomas Byrne.
The race for the coveted nomination re-ignited the contest dubbed the 'Battle of Blackrock', when Kate Feeney and Mary Hanafin went head-to-head to secure the party's nomination for the local elections. In the end, both women ran for Fianna Fail and both were selected.
Although Dun Laoghaire- Rathdown is a four-seat constituency, it's effectively a three-seater, as sitting TD and Ceann Comhairle Sean Barrett will be automatically re-elected to the next Dail.
However, although Cormac Devlin has won the convention, party bosses have the option of adding another candidate to the ticket. As Fianna Fail has under 23pc of female candidates to date, either Mary Hanafin or Kate Feeney may yet get the nod.