Catherine Connolly has accused her only rival for the presidency of making a "scurrilous" accusation that she had "insulted" allies.
She faced Fine Gael candidate Heather Humphreys on RTÉ Radio 1's Drivetime, during which Ms Humphreys said people had a "clear choice" in the election: "Do you want a president that hasn't fallen out with or insulted our allies?"
The question referred to comments previously made by Ms Connolly, when she referenced Germany's militarisation during the 1930s under the Nazis when discussing the country's current defence spending.
Independent candidate Ms Connolly replied, saying: "Normalisation of genocide is absolutely unacceptable to me, and the vast majority of the people in Ireland.
"Countries were pointed out by me that were very supportive of Israel and America's role in it."
The two presidential hopefuls faced each other for the first time since the third candidate, Fianna Fáil nominee Jim Gavin, dropped out of the race on Monday.
The two were quizzed by presenters Sarah McInerney and Cormac Ó hEadhra about their political records and plans for the presidency.
Asked about her role in the government which implemented harsh austerity measures following the global financial crisis, Ms Humphreys said: "Maybe things could have been done differently.
"When you look back, I think, maybe, we could have spent more money sooner.
"I'm not saying we got everything right but, at least, we stepped up to the plate."
Ms Humphreys served as a TD in the Dáil between 2011 and 2024, including in a number of cabinet positions.
In 2016, she was made Minister for Arts, Heritage, Regional, Rural and Gaeltacht Affairs, but could not speak the Irish language fluently despite being responsible for Ireland's Irish-speaking regions.
She told the Radio 1 programme that she did not follow through on her commitment to improving her grasp of the language because of Brexit, explaining: "I moved into the Department of Business.
"I was dealing with Brexit, I was dealing with the pandemic, I genuinely didn't have time."
But said she was committed to "learning Irish, refreshing my Irish".
Ms Connolly, who is supported by a coalition of left-wing parties and other independent TDs, was also questioned about her work during Ireland's recession.
At the time, she was a barrister and sat on Galway City Council, she was asked whether it was true she represented banks in repossession cases.
She replied: "It's true that a barrister takes every brief that they get, unless there's a conflict of interest, and so there's an onus and an obligation on a barrister who's independent and independently employed to take briefs."
Discussing the possibility of a united Ireland, candidates were asked about how they would work with different communities in Northern Ireland.
Ms Humphreys, who is from a Protestant background, said she would tell Unionists: "I am the perfect example of living in a country, from a minority tradition.
"I got an opportunity, this country made me what I am. It has given me everything I have."
Ms Connolly said she would "absolutely love" to see a united Ireland during her tenure as president but said she would leave the issue of a border poll on unification "to the political parties".
On the issue of defence spending, both said more support was needed for the Defence Forces.
But when Ms Connolly was given the final word on the topic, she said: "I think we need to use our voice for peace in the world.
"We need to speak truth to power, whether that's to Russia or whether that's to Israel and America."
Ms Humphreys quickly jumped in saying "that's what Chamberlain said", comparing the comments to a 1938 speech made by former British prime minister Neville Chamberlain following the signing of the Munich agreement.
That deal allowed for the annexation of part of Czechoslovakia by Nazi Germany as part of the failed policy of appeasement.
In a lighter final question, the pair were asked about their "party pieces" after a video of Ms Connolly playing football with children went viral.
The Galway TD said she was "disappointed" she "only managed about 10" saying "I used to be able to do 100."
In contrast, Ms Humphreys said she "didn't really have a party piece" instead her best skill was "listening".
Earlier, Ms Connolly said Fine Gael are "absolutely scared" of the momentum behind her campaign.
The Independent candidate also said she has spent her whole life standing up for women and said people know her as that person.
"I've never changed," she said.
Speaking to reporters, Ms Connolly said she would "absolutely not" be employing anyone who is on the sex offenders' register.
Her remarks come following a radio interview on Newstalk, where she was asked a hypothetical question whether she would consider hiring a convicted rapist to work in Áras an Uachtaráin. Ms Connolly said that she would "have to think about it".
Earlier, Minister for Health Jennifer Carroll MacNeill described those comments as "completely unacceptable".
The Fine Gael minister said she did not understand how there was any ambiguity about the matter.
It followed previous questions to Ms Connolly about the employment of a woman in 2019, who had been convicted of possessing a weapon and ammunition.
Ms Connolly had previously said the woman had been "absolutely perfect" for the job.
When asked during an interview about the possible scenario of hiring a convicted rapist to work in the Áras, she said she "would have to reflect on that".
"I'd have to think on that," she said.
"As a woman, I react. So obviously, I would have to reflect," said Ms Connolly.
Minister for Health Jennifer Carroll MacNeill said she doesn't 'understand how this is even a question'
Speaking at the launch of Ruhama's annual report, Minister Carroll MacNeill acknowledged that there is a criminal justice system where people with convictions are rehabilitated, "but we don't allow people with sex offences to work in schools for example, we don't allow people with gun convictions to work in the Houses of Parliament," she said.
"This should be obvious, and it should be obvious to any parliamentarian, and obvious to anyone running for the role of president," she said.
"I don't understand how this is even a question," Ms Carroll MacNeill added.
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