Fine Gael's Deirdre Clune is in danger of losing her Cork South Central seat to Dan Boyle of the Green Party, according to an MRBI/Evening Echo poll.
The poll also indicates that Fianna Fail will hold onto its three seats in the constituency.
This strong Fianna Fail performance suggests the party could be on course to form the next Government, and will be a blow to Fine Gael leader Michael Noonan.
Fianna Fail has managed to increase its first preference vote in the constituency from 43% in 1997 to 51%, according to the poll published this afternoon.
Conducted among 400 people earlier this month in Cork South Central, and excluding undecided voters, the poll predicts Health Minister MIcheal Martin and Simon Coveney will be elected on the first count.
Michael Martin secured a massive 29% of the first preference vote, and Simon Coveney 18% - more than a quote in each case.
The poll predicts that Fianna Fail's three candidates will get a combined first preference vote of 51%.
This would secure three quotas for the party with Deputies John Dennehy and Batt O'Keeffe being elected in later counts.