Support for Fine Gael has dropped by four percentage points to 19%, the latest Sunday Times/Behaviour and Attitudes Opinion Poll suggests.
The survey of 936 eligible voters over 13 days up to last Tuesday indicates that Sinn Féin commands the strongest level of support on 34%, which is unchanged since last month.
Support for Fianna Fáil has risen by four points to 25% while the Green Party is unchanged on 5%.
Labour gain one point to stand at 4% while there were single point gains too for both the Social Democrats and PBP/Solidarity who are each on 2% support.
There was a four-point fall in support for Independents which was gauged at 8% while Aontú is on 1%.
This opinion poll has a margin or error of plus or minus 3.3%.