Fianna Fáil has overtaken Fine Gael in an opinion poll for the first time in almost eight years, according to a survey of voters for the Sunday Times.
The Behaviour and Attitudes research suggests a substantial drop in support for the party that won the most seats in the General Election.
Fianna Fáil has not appeared as a leading party in an opinion poll since before October 2008.
This sample of 926 voters over ten days up to Wednesday last estimates Fianna Fáil's support at 26%.
This shows an increase of four points on the previous poll carried out just before the General Election in late February.
The poll also suggests a slump in Fine Gael support - the party is down seven points to 23%.
Sinn Féin is up two points to 17% while there is an increase too in support for the Independent Alliance, up three points to 8%.
Independents are unchanged on 10%, as are Labour on 4%. The AAA/PBP are also on 4%, down one point on the last poll.
The Greens and the Workers Party are both on 3%, the Social Democrats are on 2% and Renua is at 1%.
The poll has a margin of error of just over 3%.