Sinn Féin's Pearse Doherty has received 13,719 votes in the Donegal South West by-election and is in poll position to take the seat where the quota is 17,213.
Fiana Fáil's Brian Ó Domhnaill received 7,344 votes, Fine Gael's Barry O'Neill got 6,424, Independent candidate Thomas Pringle won 3,488 votes and Labour's Frank McBrearty got 3,366, votes.
The independent candidate, Ann Sweeney, received 133 votes so she has been excluded and her votes are being redistributed.
A final result will be declared later today, but Government ministers conceded defeat after first-preference votes were counted.
Sinn Féin president Gerry Adams, whose party opposes the drastic cuts aimed at saving the crippled economy, said: “It appears the people have responded and they have made a stand alongside Sinn Féin.”