A gay Irish senator is the favourite to become Ireland's next president, while former IRA commander Martin McGuinness is in third place, an opinion poll said Saturday.

Senator David Norris had the backing of 21 percent of those surveyed in a Red C/Sunday Business Post poll ahead of the October 27 election to succeed President Mary McAleese.

Norris has only recently re-entered the race, having earlier abandoned his presidency bid when it emerged he had written to Israeli authorities pleading for clemency for his former partner, Ezra Yitzhak.

Yitzhak was convicted in 1997 for the statutory rape of a 15-year-old Palestinian boy in 1992.

Norris is still seeking the nomination of 20 parliamentarians or four local councils to ensure his name is on the ballot paper for the election.

Nominations close on September 28.

Second in the poll is former Labour party minister Michael D. Higgins with 18 percent, and third is Sinn Fein's McGuinness, who has stepped aside as Northern Ireland's deputy first minister, on 16 percent.

McGuinness was officially confirmed on September 18 as the socialist republican Sinn Fein party's candidate.

Behind them is MEP Gay Mitchell of Prime Minister Enda Kenny's Fine Gael party and independent and former Special Olympics chairwoman Mary Davis, each with 13 percent.

Independent Sean Gallagher is on 11 percent and former MEP and 1970 Eurovision song contest winner Dana Rosemary Scallon, who is also still seeking an official nomination, is on six percent.

The outgoing president, Belfast-born McAleese, has served two seven-year terms in the largely ceremonial post of president.

Under Ireland's proportional representation system transfer votes will be crucial, the Sunday Business Post said, adding that the poll data suggests both Norris and McGuinness will have difficulty securing them.

In what is expected to be the most crowded field ever, the newspaper says the outcome is "entirely unpredictable" as the race is "volatile, confused and completely wide open".