A hung parliament is widely predicted after voters went to the polls in the Republic.
Such is the voter schism it threatens to blow apart a duopoly enjoyed for more than 80 years by the currently ruling Fine Gael party and the main opposition party Fianna Fail.
Bitter rivals since Ireland's Civil War - despite little difference in their conservative policies - the parties who swapped power for generations may be forced into a historic "grand coalition".
The tectonic shift could also open a definitive right/left divide in the Dail for the first time since the foundation of the Irish State.
Opinion polls show little chance of the Fine Gael/Labour coalition being returned to power on its own.
Other possibilities include a minority Fine Gael Government, supported by arch-enemies Fianna Fail, or a rainbow coalition of Fine Gael, Labour and some smaller parties.