THE Taoiseach and the Fianna Fail leader have been conducting a series of video-taped "dry runs" with their respective advisers for tonight's hour-long televised head-to-head debate on RTE.
The debate is seen on both sides as an important means of swaying the "marginal" voters who have not finally made up their minds on who to support in Friday's election.
The huge audience which the debate between the Tanaiste, Mr Spring, and the Progressive Democrats leader, Ms Mary Harney, attracted on Monday night has added weight to tonight's exchanges between Mr Bruton and Mr Ahern. It is estimated that more than half a million people tuned in to Monday night's encounter - the largest audience for any programme on the election since the campaign began.
Tonight's debate, chaired by presenter, Miriam O'Callaghan, begins with a two-minute address by each leader. They will read from auto-cue, a facility not used by Mr Spring or Ms Harney.
It is understood that both men will stand for this section of the programme, and then take their seats to pursue a debate covering five main areas.
The chief issues are the economy, Northern Ireland, crime, alternative options for government, and their individual strengths as putative Taoiseach. They will outline and discuss the central distinguishing features of the alternative coalitions and how they would, as leaders, manage the differing views and ideologies in those blocs.
The debate on the economy will encompass taxation, employment and poverty. Mr Bruton and Mr Ahern will also be expected to outline their personal vision for Ireland and their individual strengths in realising that perception.
Ms O'Callaghan said last night that she will act as a "facilitator" rather than an inquisitor, to allow the two politicians to express their views.
The debate will conclude with a one-minute address by each leader.
Sources in both parties said they view tonight's contest as a substantial opportunity to attract the last of the "don't-knows" which make up about 12 per cent of the electorate, according to the latest opinion polls. It is also an 11th-hour chance to present themselves as statesmen.
Barring a gaffe by either side, however, it is not expected that they will inflict undue damage on each other. Both men spent some time yesterday, and will do again today, preparing for the event.