Mr Kelleher, meanwhile, said he would be engaging with party colleagues ahead of the vote.
“The purpose of this is to ensure that we have an interrogation of the candidates, that we have an interrogation of ideas and values, and that we put forward a candidate that actually reflects the Fianna Fail values that we want to take into the campaign.”
Speaking to RTÉ’s Six One News, he said: “I think it’s important in a democratic party like Fianna Fail, that we do have a healthy debate.”
Asked about whether he believes he will be successful, given that Mr Gavin had 31 public endorsements when only 36 is needed for a majority, Mr Kelleher said: “That’s the beauty about the process – in the sense that it is going to be a secret ballot.”
The MEP rejected claims that a vote for him would undermine Mr Martin’s leadership and added that he was unaware of Mr Gavin’s interest when he first approached the idea of running.
Asked if he would not have put himself forward if he had known about the leadership’s support for Mr Gavin, Mr Kelleher said:
“I still believe that there should be a contest. I don’t believe in coronations.
“I think we have to get people into the ring. They have to be able to present and articulate their views, to express themselves.”
Pressed on whether he was saying that Mr Gavin could not do that, he replied: “I can only speak for myself. I speak regularly. I engage with colleagues, I have been debating my entire life. I stand on my record.”
Meanwhile, former weather forecaster Joanna Donnelly and Riverdance star Michael Flatley announced they were no longer pursuing their bids for the office.
Mr Flatley said he had to put his family and health first, adding: “I feel I can better serve the Irish people by continuing my work promoting Ireland and Irish culture globally.”
Ms Donnelly told supporters she came to understand she was “underprepared” for a tilt at the Áras, saying in a social media post: “I was naive to think I could meet the challenges of the campaign.”
The presidential election will be held on Friday October 24.