Independent Senator Gerard Craughwell has withdrawn from the presidential race.
He had been one of the first to express an interest in running against Michael D Higgins.
In a statement today, however, he claimed to have achieved his goal of opening up a conversation about the nomination process.
Anyone hoping to secure a nomination need at least 20 members of the Oireachtas or at least four local authorities to back their bid.
Senator Craughwell said any system that prevents candidates other than the incumbent from running is 'profoundly undemocratic'.
However, he welcomed the news that Sinn Féin will put forward a candidate, and that Fianna Fáíl councillors will be able to nominate independent candidates.
He said: "To ensure that there would be a presidential election in 2018, I put myself forward as a potential candidate. In doing so I opened up what has been the first serious national conversation on the presidential nomination and election process.
"I will now stand aside and take no further part in the process other than to wish each and every candidate every success in their campaign."
Senators Joan Freeman and Pádraig Ó Céidigh, former GAA president Liam O'Neill, and artist Kevin Sharkey are among the others who are considering an Áras run.