Sinn Fein Senator Pearse Doherty will trounce Fianna Fail in the Donegal South West by-election, an opinion poll suggests.
The Red C survey shows Mr Doherty taking 40% of first-preference votes - more than double Fianna Fail's Senator Brian O'Domhnaill, who is expected to take just 19%.
If correct, the result would deliver a potentially lethal blow to the Government, which is struggling to keep control of the Dail with a razor-thin majority.
Voters finally go the polls on November 25 to replace the seat left empty by Fianna Fail's Pat "The Cope" Gallagher after he was elected an MEP 18 months ago.
Mr Doherty forced the by-election by taking the Government to the High Court.
The Red C poll predicts Mr O'Domhnaill will suffer relatively poor transfers in what has always been considered a Fianna Fail stronghold.
He is unlikely to even trouble Sinn Fein on the second count, it predicted.
Fine Gael's Barry O'Neill and Labour's Frank McBrearty Junior are set to take a similar share of the first-preference vote - 15% and 14% respectively.
But transfers suggest Mr McBrearty, who was framed by the Garda for a murder that never happened, will end up ahead.
In a further blow to the senior coalition party, Fianna Fail's first preference votes would plunge to 19% - down a third from from 2007 - in Donegal South West if a general election was called, according to the poll.