Ireland's ruling coalition has been ousted by voters angry at the country's uneven recovery, leaving Prime Minister Enda Kenny facing the unpalatable prospect of trying to secure a deal with his biggest rival.
His government appeared to be the latest victim of European voters' growing antipathy to mainstream politics, hit by a backlash against years of austerity and a perception that Ireland's poor are not benefiting from the fastest economic growth in Europe.
Exit polls on Saturday suggest the only viable option may be a problematic alliance of old rivals Fianna Fail and Kenny's Fine Gael - although even their combined support was set to fall below 50 per cent of the vote for the first time.
If neither side is able to form a government, however, fresh elections would have to be called.
"The government of Fine Gael and Labour cannot be returned," Kenny told journalists late on Saturday.
"I've a duty and a responsibility to work with the decision that the people have made to provide the country with a stable government, and that I intend to do fully and completely."
The centre-right Fine Gael captured 26 percent of first preference votes when 38 of 40 constituencies were counted.
That is far below the 36 percent it won five years ago and the 30 per cent opinion poll rating it had at the start of campaigning.
Current coalition partner Labour was in line to win just seven per cent of the ballot, which spending minister Brendan Howlin said meant they were out of the equation for the next government.
Fianna Fail was set to rise to 25 percent.
"It was certainly worse than my worst fears," Health Minister Leo Varadkar, a senior member of Fine Gael.
He said there was very little support for a Fine Gael-Fianna Fail coalition, but he refused to rule it out.