Announcing that he would no longer seek nominations to contest the race, the independent senator said he had shown it is possible for a gay person to be seen as a viable candidate for the highest office in the land.
Mr Norris announced his decision outside his Georgian home in Dublin, following days of controversy over a 1997 letter in which he sought leniency in the sentencing of Ezra Yizhak Nawi, who was convicted of statutory rape.
Mr Norris said he “did not regret seeking clemency for a friend” but added: “I do regret giving the impression that I did not have sufficient compassion for the victim of Ezra’s crime.”
He said: “I accept that, more than a decade and a half later when I have now reviewed the issue, and am not emotionally involved, when I am not afraid that Ezra will take his own life, I see that I was wrong.”
Remaining candidates last night paid tribute to Mr Norris, praising his work on rights issues over the years.
Opinion polls showed Mr Norris was the front-runner in the race. But he had secured just 15 of the 20 Oireachtas signatures needed for the nomination.
In a fatal blow to his chances, three independent TDs on Monday night withdrew their support.
Left with little option but to withdraw, Mr Norris said his candidacy had made it clear that “the whole question of the way in which candidates are nominated must be examined”.
Afterwards, he called for a clean campaign to save the remaining candidates and their families having to go through what he did. “It would be terrible for those people if this sort of thing happened.”
Mr Norris said that while he believed there was no “personal hatred” of him, people believed he represented a liberal agenda and that, “if I could be taken out of that equation, that liberal agenda could be reversed”.
Asked if he believed it was wrong to send the letter, he said: “If it is a flaw or a fault, it is certainly not illegal.”
He described Mr Nawi as “the love of my life”, adding: “You don’t stop loving somebody, whatever their faults are.”
Mr Norris said he only found out about the statutory case after the conviction and, while he did not regard Mr Nawi as a boyfriend or partner at the time, he travelled to Jerusalem for an appeal hearing.
Senior members of Mr Norris’s election team resigned last Friday, and he said that while he was very proud of them, “they are not so proud of me”.
He said he was “extremely sorry” for the “level of hurt” they felt because they believed details of the letter had been concealed from them.
Labour’s presidential candidate, Michael D Higgins, paid tribute to “the grace of Mr Norris’s statement” and said it must have been a “difficult decision”.
Independent candidate Seán Gallagher said: “On a personal and a human level, I feel for him, his friends and supporters. I would like to acknowledge the work he has done in campaigning for many important issues throughout the years.”