Micheál Martin is still the most popular leader in the country, despite a big drop in support for his party.
The latest Ipsos/MRBI poll in today's Irish Times suggests 26% of voters now back Fianna Fáil, down seven points from the last comparable poll in July.
This means the Soldiers of Destiny are neck and neck with Fine Gael, whose support has increased by two points.
Sinn Féin is on 19%, Labour is on 5% and independents and others have risen slightly to 24%.
Anti-Austerity Alliance-People Before Profit, the Social Democrats and the Independent Alliance have seen marginal changes in support.
Taoiseach Enda Kenny is only the second most popular leader in the country, at 29%, while his Fianna Fáil counterpart is on 39% approval.
Gerry Adams and Brendan Howlin are the favoured leaders of 28% and 21% of voters respectively.
The survey was carried out on Monday and Tuesday of this week among a representative sample of 1,200 voters.
The Irish Times said the margin of error is plus or minus 2.8 per cent.
