Sean Gallagher says it took him a long time to get over the Tweetgate controversy in the 2011 Presidential election.
The businessman has admitted he was unconvincing in his response when a fake tweet was put to him during a Presidential debate.
Mr Gallagher had been leading in the polls until then and has since received an apology and a sizeable lump sum as part of a settlement with RTÉ.
Mr Gallagher is running for President again and feels he was unfairly treated last time around.
He said: "Live on air you get thrown, and unfortunately that happened, people switched and I had to spend the last six years fighting that case.
"I wouldn't say I'm scarred, but I felt in my heart I had to come back and get justice and fairness."
Mr Gallagher has said he will use the Presidency to push for a united Ireland if he is elected.
The businessman has told the Times Ireland edition that partition "hasn't served Ireland well in the past, and it won't in the future".
He says that as President, he would campaign for a united Ireland to bring communities and individuals together.
