European Diary/Denis Staunton: These are crucial days for the Taoiseach and for Ireland's EU Presidency, as Mr Ahern visits 23 European capitals in his search for agreement on the constitutional treaty. The pace is hectic, taking him to Cyprus tomorrow, to Greece, Malta and Italy on Thursday and to Spain and Portugal on Friday.
In personal and political terms, the prize is great: agreement on the treaty at next month's summit would confirm the Irish Presidency as a triumph, restore Ireland's reputation within the EU and enhance the Taoiseach's reputation as a master of the art of conciliation.
The odds favour a deal, not least because a second failed summit would damage the treaty's credibility so greatly as to call into question the entire constitutional project. A change of government in Spain has removed an important obstacle to agreement on the sensitive issue of voting weights in the Council of Ministers and Irish officials see the shape of a compromise on many other unresolved questions.
Potential pitfalls remain, however, notably in extending qualified majority voting to policy areas hitherto decided by unanimity. Mr Tony Blair's decision to call a referendum on the treaty has limited his room for manoeuvre, while more integrationist governments fear that retaining too many national vetoes could make the EU unworkable.
During his tour of capitals, Mr Ahern will also consult other leaders on who should succeed Mr Romano Prodi as President of the European Commission. Three candidates have already indicated an interest in the job: Belgium's prime minister, Mr Guy Verhofstadt; the External Affairs Commissioner, Mr Chris Patten; and the outgoing President of the European Parliament, Mr Pat Cox.
As President of the European Council, the Taoiseach is responsible for finding a consensus, but he is inhibited from promoting a candidate. Presidency officials say that this inhibition is reinforced by Mr Ahern's determination that nothing should undermine his role as an honest broker in the treaty negotiations - the Presidency's over-riding priority.
Contrary to rumours sweeping Strasbourg last week, Mr Cox's decision to step down from the European Parliament was not part of a deal with the Taoiseach; in fact, nobody in Dublin was given advance notice of the move. Indeed, there may be less than meets the eye to Mr Ahern's promises of support for Mr Cox should he emerge as a likely Commission president. Diplomatic sources suggest that the Taoiseach's promise amounts to no more than a commitment to formally nominate Mr Cox if the other EU leaders choose him as Mr Prodi's successor.
Commissioners are not allowed to take instruction from national governments, but it is in every state's interest to have one of its nationals in senior EU positions. This is particularly true for small countries, which can benefit from a level of access and intelligence that would otherwise be impossible.
Some Irish officials dismiss Mr Cox's chances of securing the appointment,and believe that the Taoiseach should use his wiles to offer subtle support to Mr Patten as Ireland's next best option. Mr Patten knows and understands Irish interests well, and enjoys warm relations with Mr Ahern and the Minister for Foreign Affairs, Mr Cowen.
The choice of Commission President could become entangled with the treaty negotiations, particularly if France and Germany make support for Mr Patten conditional on extracting compromises from Britain. Mr Patten's entry into the race is good news for Mr Blair, giving him an unexpected bargaining counter in the treaty talks.
If the treaty is agreed, but leaders remain deadlocked on Mr Prodi's successor, attention could turn to Mr Ahern himself as the hero of the hour. The Taoiseach has stated a number of times that he does not wish to move to Brussels, but late at night in the conference chamber, flush with the success of his deal-making, nothing should be ruled out.