The former MEP Ms Dana Rosemary Scallan will not say whether she will contest a presidential election until President McAleese declares whether she will seek a second term.
Mrs McAleese is widely expected to declare in the coming weeks that she will seek a second seven-year term of office.
Ms Scallan's brother and campaign manager, Mr John Browne, said last night that she had not yet decided to seek a nomination.
"She's going to make her mind up after the President declares her position," Mr Browne said.
Ms Scallan was an unsuccessful candidate in the 1997 presidential election that brought Mrs McAleese to power.
After losing her seat in the European Parliament in June, she has hinted in recent weeks that she will again run for the presidency.
"She's not seeking a nomination. She's not made that decision yet," said Mr Browne. Reports that she will declare her candidacy today were not true, he said.
Should Ms Scallan contest an election, she is likely to campaign against the draft EU constitution on the basis that it supersedes the Irish Constitution.
Mr Browne said his sister was examining the provisions in the Constitution which oblige the President to uphold the primacy of the Constitution in all matters.
While Ms Scallan would require the support of four county councils to receive a nomination in a presidential election, Mr Browne said she was not canvassing county councillors at present.
