The voting strengths of the two camps in the Fine Gael leadership battle appeared evenly balanced late last night.
The party is now split down the middle on the motion of no confidence in Mr Bruton.
Each side now seems likely to have a minimum of 30 votes at the 72-member Parliamentary Party meeting this afternoon. A small number of crucial votes are undecided.
The meeting to decide on Mr Bruton's future as leader of Fine Gael will begin at 2.30 p.m. today and is expected to continue for some hours.
The first matter to be discussed concerns a request by Mr Alan Shatter TD that the voting figures be made public. He wrote this week to the party chairman, Mr Phil Hogan, who will chair the meeting, asking that this step, unprecedented for Fine Gael, be taken.
Some 72 members of the party - 53 TDs, four MEPs and 16 senators - are entitled to vote. Ms Avril Doyle, an MEP and a senator, has one vote.
Following that, the proposer and seconder of the motion of no confidence in Mr Bruton, Mr Michael Noonan and Mr Jim Mitchell, will speak.
Any member of the party who wishes to speak after that may do so, and there are no time restrictions.
On the last occasion that Mr Bruton's leadership was voted upon in November the meeting lasted 31/2 hours and 37 people spoke.
It is expected that considerably more people will contribute today, and the meeting will last far longer.
Mr Bruton is scheduled to hold a press conference following the meeting.
The Irish Times has confirmed that at least 30 people have committed themselves publicly or privately to the no-confidence motion tabled by Mr Noonan and Mr Mitchell.
A further 27 have committed themselves to supporting Mr Bruton, while the intentions of 16 could not be ascertained with confidence.
It emerged last night that a frontbench member, Ms Frances Fitzgerald, has told colleagues she will support Mr Bruton, despite earlier predictions that she would vote with the dissidents.
However, another frontbench member, Mr Jim O'Keeffe, is expected to bring to at least six the number of senior spokespersons opposing Mr Bruton.
Those on the front bench declared against him are Mr Noonan, Mr Mitchell, Mr Alan Shatter, Mr Michael Finucane and Ms Deirdre Clune, with the intentions of Mr Jim Higgins, Ms Avril Doyle and Mr Paul Connaughton unknown. The other 13 frontbench members are expected to support the leader.
Those whose intentions could not be ascertained last night were: Ms Monica Barnes, Mr Sean Barrett, Mr Liam Burke, Mr Paddy Burke, Mr Paul Coghlan, Mr Michael Joe Cosgrave, Mr Simon Coveney, Mr Dino Cregan, Mr Joe Doyle, Mr Tom Enright, Mr Tom Hayes, Mr Jim Higgins, Mr Jim O'Keeffe, Ms Madeleine Taylor-Quinn, Mr Michael Ring and Mr David Stanton.
Mr Dan Neville, the only Limerick party member in favour of Mr Bruton, said: "Some people in Limerick are going to kill me and some won't mind. John Bruton has always been very supportive of the work I do, particularly in the areas of mental health and suicide.
"One opinion poll won't change my mind. He represents a lot of the values that should be in a leader. Even if the others have those values, if you move a leader with those values it can seem like you're not supporting those values."