Fine Gael may retain its seat in the Dublin Bay South constituency as James Geoghegan is leading in the opinion polls.
An Irish Times/Ipsos MRBI opinion poll shows the Fine Gael councillor is the first choice for 27% of voters in the Dublin Bay South constituency.
The by-election, set to take place on July 8, was triggered by former Housing Minister Eoghan Murphy's resignation.
Labour senator Ivana Bacik is polling at second place, with 22% of the vote.
Sinn Fein senator Lynn Boylan is at 13%, while Fianna Fail candidate Deirdre Conroy has just 10%.
Green Party candidate Claire Byrne has 11% of voters' support, while Social Democrats candidate Sarah Durcan is polling at 5%.
Independent candidate Mannix Flynn also has the support of 5% of voters, while Aontu candidate Mairead Tóibín is polling at 3%.
People Before Profit's candidate Brigid Purcell is at 2% while the National Party's Justin Barrett is at 1% along with Independent Peter Dooley, who is also at 1%.
The remaining candidates received less than one per cent support.
The survey was conducted through personal in-home interviewing in the constituency between last Friday and Sunday, among a sample of 500 adults at 50 points throughout the constituency.
The accuracy level is estimated at approximately plus or minus 4.4%. The level of those expressing no view as to their voting intentions was 18%.
