Cllr Áine Brady was last night selected by a Fianna Fáil convention to run for the party in next month's by-election in Kildare North.
Ms Brady, the sister of the Government Chief Whip, Mr Tom Kitt, and the Galway East TD, Mr Michael Kitt, beat her closest challenger, Naas-based Cllr Michael Fitzpatrick, by six votes.
The selection convention, which was decided by 60 delegates, was held in the Glen Royal Hotel in Maynooth and was chaired by the Minister for Finance, Mr Cowen.
In the first round of voting Cllr Brady received 27 votes, Cllr Fitzpatrick 16, Cllr Willie Callaghan four, Mr Anthony Greevey one and Cllr Liam Doyle 12.
Following the elimination of Mr Greevey, Cllr Doyle's vote increased to 13.
After Cllr Callaghan was eliminated, his four votes divided equally between Cllr Brady and Cllr Fitzpatrick, bringing them to 29 and 18 votes respectively.
The issue was decided by the distribution of Cllr Doyle's 13 votes.
Cllr Fitzgerald received nine, bringing him to 27, but Cllr Brady received four, which brought her to 33.
Accepting the party's nomination for the March 11th by-election Cllr Brady said she intended to be "the first-ever woman TD from Kildare".
Paying repeated tributes to the former minister for finance, Mr Charlie McCreevy, Mr Cowen said he had repeatedly "delivered" for the Kildare North constituency during his time in national politics.
Calling on voters to support Cllr Brady, Mr Cowen urged them not to leave the Government without representation in the constituency.
"The opposition can only talk, but the Government is the one that can deliver. Áine Brady is the only candidate that can walk into Leinster House and have access to the levers of power," he said.
In a clear acknowledgment that the by-election will be decided by transfers, the Minister urged Fianna Fáil supporters in the constituency to seek transfers wherever possible.
The other candidates in the by-election race are Labour's Cllr Paddy McNamara, Fine Gael's Mr Darren Scully, a member of Naas Urban District Council, Progressive Democrat Senator Kate Walsh, the Green Party's Cllr J.J. Power, who sits on Kildare County Council for the Naas electoral ward and who is a brother of Fianna Fáil Minister of State, Mr Seán Power, and the Independent Leixlip-based councillor, Ms Catherine Murphy.
The Fianna Fáil election campaign will be led by Mr Cowen. Last night the Deputy Director of Elections, the Minister for Defence, Mr O'Dea, said it would be virtually inconceivable if Fianna Fáil had no representation in the constituency that had been represented for so long by Mr McCreevy.