Sinn Féin is being widely tipped to top the poll when the European election results are counted in Northern Ireland tomorrow.
The Democratic Unionist Party (DUP) is braced to suffer a major hit in the election, which saw a low voter turnout of only 42.8 per cent.
Unofficial tallies have given Sinn Féin's Bairbre de Brún a comfortable lead on the pack, holding out the prospect that it could become the first republican or nationalist party to ever top a Northern Ireland election.
The same estimates suggest the DUP has been badly hit by disaffection among its own voters in the wake of the Westminster expenses scandal and by a successful challenge from unionist hardliner Jim Allister.
The former DUP member who split from the party over its decision to enter government with Sinn Féin, and who now leads the Traditional Unionist Voice (TUV) party, is predicted to have secured more than 10 per cent of the vote.
The unofficial projections are based on estimates from party officials who watched election staff verify ballot papers at the King's Hall Count Centre in Belfast on Friday.
Official results will be declared tomorrow. Counting begins at 9am and the first results are expected by the afternoon.
It has been confirmed that 42.8 per cent of people eligible to vote cast a ballot - a major drop on the figure of 51.72 per cent at the last European election.
Turnout figures were also available for Northern Ireland's 18 Westminster constituencies, which showed that regions of unionist voting strength suffered lower turnouts than areas that are predominantly nationalist.
The highest turnout of 52.83 per cent was in the Mid Ulster area - a constituency which returned Sinn Féin's deputy First Minister Martin McGuinness as MP at the last General Election. The lowest turnout of 34.24 per cent was registered in Strangford - where Iris Robinson, wife of the DUP First Minister Peter Robinson, is MP.
The total votes polled across Northern Ireland was 488,891 from a eligible electorate of 1,141,979.
The region has seven candidates fighting for the three European Parliamentary seats.
They are Stephen Agnew of the Green Party, Jim Allister of Traditional Unionist Voice, Bairbre de Brún of Sinn Féin, Diane Dodds of the DUP, Alban Maginness of the SDLP, Jim Nicholson of the Ulster Conservatives and Unionists, and Ian Parsley of the Alliance party.
In the last European election, the DUP topped the poll with 32 per cent of the first preference votes — but there are predictions that its result on Monday could drop to 20 per cent or lower.
Other estimates suggested Ms de Brun could improve on her last European election performance of 26 per cent of first preferences. One tally showed the Ulster Unionist Party - which formed a new electoral pact with the Conservative Party prior to this election - securing more first preference votes than the DUP.
But with Sinn Féin believed to have secured a seat, the performance of the three unionist parties as they fight for the remaining two seats with the nationalist SDLP will be closely watched.