The claim of an issue with a former tenant was raised with ex-presidential candidate Jim Gavin in early September, Jack Chambers has said.
He said he would urge Mr Gavin to repay any funds still owed to his former tenant and that he had not spoken to him since Sunday.
Mr Chambers, who is Fianna Fail’s deputy leader and director of elections for the presidential election, faced questions over the vetting process for Mr Gavin.
He repeatedly said he had told the party he did not have an issue with a tenant when “that’s obviously not the case”.
“Facts changed for him,” Mr Chambers said.
Asked if the issue was first raised with Fianna Fail on September 8, the day before Mr Gavin was chosen as the party’s presidential candidate, he said “the query was raised”.
“Jim Gavin was asked about that and he said he had no issue with a tenant, and that was consistent with his position.”
He said he last spoke to him on Sunday and that he would urge Mr Gavin to pay the tenant back.
Mr Chambers said: “I obviously regret what’s after happening and disappointed that’s what emerged over the weekend.
“Everyone is disappointed, we wanted to run a strong national campaign and obviously what emerged has undermined that.”
Earlier on Tuesday, a Fianna Fail TD said the party’s parliamentarians were put under “extensive pressure” to back Mr Gavin by party leader Micheal Martin and deputy leader Mr Chambers.
Cork East TD James O’Connor said Mr Gavin “should have never found himself on the ballot paper” after the candidate spectacularly withdrew from the presidential race amid a dispute with a former tenant.
His decision to drop out shook up the presidential contest and put Fianna Fail in disarray as figures from inside and out of the party described the development as a “complete shambles”.
In a statement, Mr O’Connor said the party must “resolutely address our mistakes and political misjudgments” from the campaign, as he questioned the judgement of Mr Martin and Mr Chambers.
He said many colleagues believed nominating Mr Gavin was a “serious risk” due to his “glaring lack” of political experience.
He accused the leadership of making a “serious miscalculation” by not listening to these concerns.
Mr O’Connor said: “Jim Gavin should have never found himself on the ballot paper.
“He was there due to the extensive pressure put on Fianna Fail TDs and senators by Micheal Martin and Jack Chambers. They repeatedly phoned each member of the parliamentary party in the days before the selection convention on the 9th of September.”
Responding on Tuesday, Fianna Fail housing minister James Browne said: “Deputy James O’Connor is obviously entitled his opinion.
“We have a democratic process. Jim Gavin was duly nominated (by) the parliamentary party, so was Billy Kelleher, and Jim Gavin won that vote.
“We have a democratic process, and that’s exactly what was carried out within the parliamentary party. But this will be discussed at our parliamentary party tomorrow, as a democratic party ought to do.”
Asked who he blames for Mr Gavin emerging as the Fianna Fail candidate, Mr Browne said his selection showed “leadership”.
“Leaders should identify prospective candidates. It is maybe stranger if the leader didn’t have an opinion on who candidates should or shouldn’t be.
“I think we shouldn’t forget that Jim has a fantastic record in terms of his charity work, his work with the Defence Forces, managing Dublin (Gaelic football team).
“He clearly made a very serious mistake here, but I think we do have to be very careful too, that the presidency shouldn’t be restricted to purely elected politicians.
“Elected politicians are a lot more robust to taking questionings and things like, there’s no question about that.
“But I think the leadership showed leadership, and that’s what you would expect, and that’s what would happen in the past.”
Mr Gavin was selected to run for Fianna Fail against Fine Gael choice Heather Humphreys and left-wing Independent Catherine Connolly, who has the backing of Sinn Fein, the Social Democrats and Labour.
However, he withdrew late on Sunday night after being dogged by questions about claims he owed a former tenant thousands of euro for a rental arrangement that was not properly registered.
Fianna Fail is due to hold a meeting of its parliamentary party on Wednesday to discuss the issues surrounding its campaign.
Mr Gavin, an aviation official who was formerly a military pilot and Dublin Gaelic football manager, withdrew from the contest after acknowledging he “made a mistake”.
The Irish Independent reported claims from a tenant who said he had failed to recover more than 3,000 euro in overpaid rent from Mr Gavin 16 years ago.
Mr Martin said his party conducted “comprehensive due diligence” on Mr Gavin and, while knowing he was a former landlord, was not aware of the rent issue.
The Taoiseach said his decision to back Mr Gavin was to have a “broad-based candidate”.
He said: “I take responsibility for that and I want to acknowledge that many, many members of the party are hurting out there because of what has transpired.”
Mr Martin, who insisted it was his intention to continue leading Fianna Fail, said he was open to engaging the parliamentary party for a comprehensive review.
It has been confirmed that Mr Gavin’s name will remain on the ballot.
Any votes for Mr Gavin will be counted and then, because of the transferable vote process, that support will be distributed proportionally to other candidates, if necessary.
The presidential election will be held on October 24.
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