The Taoiseach, Mr Ahern, has expressed anger at the manner in which the Fianna Fail Cork South Central candidate, Ms Sinead Behan, was treated by RTE in the controversial broadcasting of an interview with her on local radio.
Mr Ahern discussed the issue at length with members of his parliamentary party during their weekly meeting yesterday, although he did not comment on it publicly.
Fianna Fail sources last night said there were "ethical questions" raised by the manner in which the interview was arranged and conducted.
RTE said yesterday that the broadcast of the item on Tuesday was accidental.
Listeners in the Cork area heard a 60-second "quiz" with Ms Behan. She was asked a number of questions in quick succession, to which she replied "I don't know."
She said she did not know who was the first TD elected to the constituency, which paramilitary organisation had not declared a ceasefire, nor could she say what the level of unemployment was in Cork to the nearest thousand.
She did not know who the Ceann Comhairle or his deputy was. At one point she said: "Can we stop this? I am feeling faint."
Then asked the salary of a TD, she replied: "About £34,000." Then the tape ended.
Later she called the quiz an RTE "ambush".
In a statement broadcast on E Radio 1's News at One yesterday, RTE said: "The material in question was transmitted as a result of a technical error. It had already been decided that it should not be broadcast.
"RTE accepts that the transmission caused upset and embarrassment to the candidate and apologises for the mistake."
Yesterday Ms Behan, her director of elections, the Minister for Education, Mr Martin, Mr Toddy O'Sullivan, the Labour Party candidate and Fine Gael's, Mr Simon Coveney, went on 96 FM's daily talk show - a rival to RTE's efforts in the city - to denounce the manner in which the tape had come into the public domain.
Ms Behan pleaded some confusion under an extreme and unexpected form of questioning. Her understanding, she said, was that she had been invited to participate in a formal interview.
Mr Martin said there was every chance the matter would be referred to the Broadcasting Complaints Commission. On the eve of the moratorium on by-election coverage, her main opponent, Mr Coveney, said he felt sorry about the manner in which Ms Behan had been treated.
With polling stations due to open at 8 a.m. tomorrow, Fianna Fail sources last night said the incident could work in Ms Behan's favour and would certainly not cost her support.
She and the Fine Gael candidate are running neck and neck in the polls, with transfers from Mr O'Sullivan favouring him at a rate of two to one.
Polling stations will remain open until 9 p.m. and the count begins at the Neptune Stadium 12 hours later. It is understood that the result of the first count will be known by Saturday lunchtime and the final outcome should be available by teatime.