Ireland's main opposition leader Enda Kenny has said his Fine Gael party has won a "massive endorsement" to govern after parliamentary elections.
Votes are still being counted but Fine Gael is expected to be the largest party in the Republic's parliament, without having an overall majority.
The dominant party for generations, Fianna Fail, faces a crushing defeat.
Mr Kenny said he would now work on renegotiating the previous government's 85bn-euro (£72bn) EU/IMF loan package.
The Irish Republic is the first EU member state to have received a financial bail-out to go to the polls. Mr Kenny said the "exceptional mandate" he had secured would enable him to put his case to other EU countries for changing the terms of the loan.
"I look for co-operation and support across Europe," he told Irish national broadcaster RTE, adding that he intended to make an immediate start on revisiting the terms of the bail-out in the coming week. Mr Kenny is particularly keen to reduce the 5.8% interest rate imposed on EU loans.
He said European leaders knew of the difficulties that the Irish people had with the loan package and he saw "room to manoeuvre" over the interest rate. He aimed first to speak to the European People's Party grouping of centre-right parties in Helsinki on 4 March before tackling the issue at an EU summit in Brussels a week later.
The extent of his election success was emphasised by the 17,472 first preference votes he received in his Mayo constituency in the west of Ireland. It was the highest number of first preference votes for any candidate under the Irish system of proportional representation.
RTE said Mr Kenny was now certain to be elected taoiseach (prime minister) when the Dail met on 9 March.
Outgoing Taoiseach Brian Cowen congratulated Mr Kenny, describing the opposition's vote as "outstanding".
Voters blamed Fianna Fail for the end of the "Celtic Tiger" economic boom. The party is on course to lose more than 50 of the 78 seats it secured in the 2007 election. Former junior coalition partner, the Greens, also fared badly.
Micheal Martin, who has replaced Mr Cowen as Fianna Fail leader, also congratulated Mr Kenny and said he expected Fianna Fail to fall short of the 24 seats he had hoped for.
"I was under no illusion that there was an enormous challenge ahead of us," he said. "I'm eager now to lead the party through a period of renewal and restore the trust with the Irish people."
Fine Gael is hoping to secure a majority in the 166-seat Dail but with an estimated 36% of first-preference votes, the party is expected to fall short of the required 83 seats.
A coalition with the Labour party, tipped for second place, is most likely although Fine Gael might also seek a deal with independent members of the parliament.
The party's director of elections, Phil Hogan, said he was optimistic of winning between 78 and 82 seats but Mr Kenny preferred to wait for the final result.
However he said that once the final outcome was clear he would form a government as quickly as he could so as not to send the "wrong signals" to other European governments.
When asked whether there were major differences between his party and Labour, Mr Kenny responded: "The people deserve a strong government and there's not an hour to be lost."
'Wipe-out' in Dublin
BBC Ireland correspondent Mark Simpson says Fianna Fail is facing almost complete wipe-out in Dublin. Its share of the vote in the capital city is estimated to be just 8%, and analysts say the party will struggle to win more than one of Dublin's seats.
Former Finance Minister Brian Lenihan has been elected but he is likely to be Fianna Fail's sole survivor in the city. His brother, former junior minister Conor Lenihan, lost his seat.
Noel Dempsey, a former Fianna Fail minister retiring from politics, said a nationwide total of 20-plus seats was all the party could hope for.
"It's looking pretty grim," he said. Another spokesman said the party had struggled in every constituency.
Sinn Fein leader Gerry Adams, who gave up his seat in the UK parliament to stand in the election and stepped down from the Northern Ireland Assembly, topped the poll in Louth, in the north-east, with more than 15,000 votes.
Sinn Fein is aiming at least to double its representation in the Irish parliament.
Mr Adams said it was on course for major gains: "I think the votes across the state show a significant amount of people support the position we have taken up."
According to the RTE exit poll, throughout the country Fine Gael won 36.1% and Labour, its traditional coalition partner, took 20.5% - its best result ever. Fianna Fail was knocked into third place on 15.1%, its worst ever result.
Sinn Fein won 10.1% while support for the Greens, Fianna Fail's junior coalition partner, plummeted to 2.7%. Other candidates, in a race with a record number of independents standing, took 15.5%.
It will take two days to complete the official count.
Many parts of the country saw a big increase in turnout on the 67% recorded in the last general election in 2007.