A SMALL number of Fianna Fail TDs will not decide their vote until moments before the ballot.
The contest is on such a knife-edge that some backbenchers were waiting to see Brian Cowen spar with the Opposition in the Dail today before declaring their intentions.
Both Mr Cowen and his challenger Micheal Martin have been in a war of words over the airwaves for the past 48 hours.
But many within Fianna Fail are still torn as to whether it is a good idea to change leaders just weeks before a General Election.
More than 20 TDs have yet to declare their intentions including Cabinet members Mary Hanafin and Dermot Ahern.
Party staff were today making arrangements for Justice Minister Dermot Ahern and Noel Treacy to vote by proxy.
Mr Ahern is in hospital after a hip operation and is unable to attend tonight's Parliamentary Party meeting.
Party sources said not every TD will speak: "If 70 TDs each spoke for five minutes then it would go on for six hours, but we don't expect that to happen.
"We're not going to put a time limit on it or limit the number of speakers. The plan is to get everything out in the open and said tonight so that this can be put behind us once and for all."
The meeting is due to start at 5.30pm with the result expected around 9pm.
Mr Cowen needs the support of 36 TDs to win the vote and stay on as party leader until after the election
This morning Mr Cowen was chairing a Cabinet meeting attended by Micheal Martin and Green Party leader John Gormley. He is also due to take Leader's Questions in the Dail.
He will be in the Dail from 3.15pm until shortly before 5pm and will have around half an hour to compose himself before the party meeting in a special room inside Leinster House.
Mr Cowen will open the meeting with a speech defending his term as Taoiseach and will outline his General Election strategy.
Minister Martin will be given an opportunity to speak early in the meeting. Two senior party members will then be agreed by both sides as tellers,but the room will not be told the vote split.