Fianna Fáil has instructed that just one candidate be chosen at the party's selection convention in the high-profile Dublin Bay North constituency.
The party is likely to await the outcome of tonight's convention, which is being held in Clontarf Castle, before deciding whether to add a second candidate.
Former minister Sean Haughey is being challenged for a place on the general election ticket by sitting councillors Deirdre Heney and Tom Brabazon, as well unsuccessful local election candidate Aileen Woods.
Ms Woods is the daughter of former Fianna Fáil minister Michael Woods and is based on the opposite side of the constituency to both Mr Haughey and Ms Heney.
Party sources say she is likely to be handed Mr Haughey's Dublin City Council seat if he is elected to the Dáil.
The selection convention is being held just weeks after Senator Averil Power shocked her colleagues by quitting the party.
Ms Power, who has not ruled out running in the upcoming election as an independent, strongly criticised members of the Fianna Fáil frontbench for their failure to campaign for a Yes vote in the Marriage Equality referendum. She also accused party leader Micheál Martin of being a "leader without followers".
Despite her departure, the party received a poll boost in last weekend's Behaviour and Analysis poll for the 'Sunday Times'.
In a letter to members of the Dublin Bay North branch, Fianna Fáil general secretary Seán Dorgan issued a diktat that just one candidate be selected at the convention.
He said the strategy was decided by the party's National Constituencies Committee, which is chaired by Cork North West TD Michael Moynihan.
Mr Dorgan pointed out that the party had moved to a one member, one vote system following a decision taken at the Fianna Fáil Árd Fheis.
Party sources say Mr Haughey, who is son of the late Taoiseach Charles Haughey, is confident that he has the numbers to win selection.
However, Mr Brabazon and Ms Heney have both been phoning delegates in recent days seeking their support.
The outcome of the Dublin Bay North poll is likely to be one of the most difficult to call in the capital.
Six sitting TDs, including two ministers, are vying for just five seats on offer.
Key to Ms Power's decision will be whether she can bring a significant portion of her Fianna Fáil support base with her as an independent candidate.