Sinn Fein today topped the poll in Northern Ireland's European elections after a collapse in support for the Democratic Unionist Party (DUP).
It is the first time a republican or nationalist party has secured the largest share of the vote in a Northern Ireland election.
Sinn Fein's Bairbre de Brun polled 126,184 votes and was elected on the first count.
But the DUP candidate Diane Dodds saw support for her party fall from 175,761 votes at the last European election to 88,346 votes.
The DUP vote was shattered as a result of a number of factors, party figures claimed today.
But the results announced at the King's Hall count centre in Belfast showed substantial support had shifted to leader of the hardline Traditional Unionist Voice (TUV) Jim Allister.
He split from the DUP over its decision to enter power-sharing government with Sinn Fein.
Today the TUV leader polled 66,197 votes, securing substantial support from the unionist electorate in his party's first major outing.
Mr Allister said unionists had signalled their opposition to Sinn Fein holding positions in government.
He said of his vote share: "That is a remarkable achievement and shows the depth of feeling that there is among many unionists who refuse to be rolled over in the era of Sinn Fein rule."
In a further dramatic development, Jim Nicholson, standing on a joint Ulster Unionist/Conservative Party ticket, performed well in what is also the first outing for the new electoral pact with David Cameron's Tory Party.
He secured 82,893 first preference votes, finishing close to the DUP candidate.
With Sinn Fein elected, the unionist parties are now in a close fight to secure the remaining two European Parliament seats in Northern Ireland.
Only 42.8% of people eligible to vote cast a ballot - a major drop on the figure of 51.72% at the last European election.
Turnout figures for Northern Ireland's 18 Westminster constituencies showed that regions of unionist voting strength suffered lower turnouts than areas that are predominantly nationalist.
The highest turnout of 52.83% was in the Mid Ulster area - a constituency which returned Sinn Fein's Deputy First Minister Martin McGuinness as MP at the last general election.
The lowest turnout of 34.24% was registered in Strangford - where Iris Robinson, wife of DUP First Minister Peter Robinson, is MP.
The total number of votes polled across Northern Ireland was 488,891, from a eligible electorate of 1,141,979.
Nationalist SDLP candidate Alban McGuinness polled 78,489 first preference votes.
Green Party candidate Stephen Agnew polled 15,764 votes, a major improvement on the party's last European performance of just under 5,000 votes.
The Alliance Party's Ian Parsley secured 26,699 votes.
DUP members reported that during the election campaign, voters on the doorsteps were angry over the MPs' expenses scandal which has gripped Westminster.
The party, including its leader and Northern Ireland First Minister Peter Robinson, was also under pressure over media reports on the accumulated earnings of DUP politicians who hold a series of separate posts.
The DUP had announced a phasing out of so-called double-jobbing during the final leg of the campaign.
But its election literature was dominated by an appeal to voters to stop Sinn Fein from topping the poll by backing Diane Dodds.
The TUV today seemed to have secured a major share of that anti-republican vote, having argued the DUP could not tell its supporters it was bent on destroying Sinn Fein while nevertheless sharing government with it.
Sinn Fein today said that despite the success of the TUV in securing substantial support, the vast majority of voters had backed parties in favour of the peace process and the power-sharing Assembly.
The party's winning candidate, Bairbre de Brun, said: "I see the vote I received as an endorsement of positive politics.
"And I think what we have seen, and want to see, is positive leadership from all parties.
"We have to tackle the scourge of sectarianism. I promise to do my part."
Sinn Fein seized 26% of the vote - slightly down on the percentage share it secured last time out.
The DUP share of the vote fell from 32% at the last Euro poll to 18.2%.
The SDLP remained on the same level as its past performance, with 16.2% of the vote.
And in a morale boosting performance for the new Conservative Party alliance with the Ulster Unionist Party, its vote rose by a half percent to 17.1%, despite predictions it would drop support.