The Northern Ireland peace process was under new pressure tonight after major election victories by the Democratic Unionists hardened demands for IRA disarmament.
The DUP, which will have five MPs in the new Westminster parliament, the highest in the party's history, immediately warned the British Prime Minister Mr Tony Blair the Belfast Agreement must go.
Sinn Féin pulled off dramatic triumphs in West Tyrone and Fermanagh and South Tyrone.
With Mr Adams winning in West Belfast and Mr McGuinness retaining his seat in Mid Ulster, the unprecedented republican one-two-three in the west of the North shattered the SDLP by overtaking the rival nationalist party for the first time.
It also shook Mr David Trimbles's Ulster Unionist Party, already devastated by big losses in key constituencies where support soared for his bitter opponents in the DUP.
The Ulster Unionists ousted Mr Robert McCartney in North Down, regained South Antrim and just held East Antrim, but the party paid a big price by sticking by the Agreement and sharing power with republicans without IRA disarmament in the face of growing Protestant anger.
The First Minister, who has already pledged to resign if the IRA do not begin emptying their arms dumps, needed police protection from a hostile and screaming crowd when he left Banbridge, Co Down tonight after his Upper Bann majority of 15,000 was shredded.
The DUP came to within 2,000 votes of defeating him.
Losing West Tyrone and North Belfast was expected, but defeats in Strangford, East Derry, and particularly Fermanagh-South Tyrone by the narrowest of margins - just 53 votes - was a huge blow, and confirmed a developing drift away to the anti-Agreement side.
The Fermanagh-south Tyrone result may be challenged in the High Court over Unionist claims of after hours voting in a republican area of the border constituency, but these crushing defeats are bound to heighten the pressure on his leadership of a party in deepening crisis.
The SDLP also suffered big hits from Sinn Féin who got massive support from first time voters. Ms Brid Rodgers losing West Tyrone was a major setback which will also have serious implications for a party in electoral trouble.
With the overall Sinn Féin and DUP vote up and likely to be consolidated and probably strengthened in next week's local government election results, the Unionist demands on Mr Blair to urge the IRA to disarm will reach new levels when he returns to Belfast later this month.
As First Minister, Mr Trimble will also resist demands to lift the ban on Sinn Féin's two ministers, Mr McGuinness and Ms Bairbre de Brun attending cross border meetings.
But Mr Adams tonight insisted that Mr Blair held the key to resolving the outstanding issues, which also included policing and demilitarisation.
He said: "It is a challenge for Mr Blair. The chickens for unionism are coming home to roost, because this is a society going through change. It can be quite difficult, particularly when you have the DUP exploiting fears, using the Agreement in their battle for the leadership of unionism.
"Mr Blair is in for a historic second term. Are the rights of nationalists and all those who voted for the Good Friday Agreement now being going to be filtered through a prism of DUPism?"
Deputy First Minister Mr Seamus Mallon who faced a strong Sinn Féin challenge in Newry-Armagh said: "It is certainly clear that a large number of people in this electorate reacted emotionally.
"But efforts to ensure we get real reconciliation will not cease and we are not going to allow the new dispensation to evaporate or die because of some elections results." PA