WITH political opponents tightening the screw and members of his own Cabinet hinting at less than whole-hearted support, Taoiseach (Prime Minister) Bertie Ahern this week went to court in a bid to block the Mahon Tribunal inquiring into some aspects of his personal finances.Ahern, citing vital constitutional privilege, launched a High Court challenge on Tuesday into certain banking transactions conducted through his accounts in 1993 and 1994.The case, in which judgment was unlikely to be delivered for several weeks, is being heard by three judges including High Court president Mr. Justice Richard Johnson in a special Divisional Court which sits only to deal with major cases of significant constitutional or legal importance.The tribunal, which started its business 10 years ago, is probing allegations of corrupt links between well-placed politicians and construction industry bosses.Mahon has ordered Ahern to produce 150 documents relating to financial advice given to him by a financial consultant and former chief operating officer of Bank of Ireland Corporate Banking, Paddy Stronge. Ahern claims the documents are legally privileged.While the court was still in session Ahern faced questions in the Dail (Parliament) from opposition leaders about his legal challenge and his obligations to the tribunal.However, it was understood that, despite Opposition pressure, he would not address conflicts between his evidence and that given by a former secretary, Grainne Carruth, about sterling lodgments.Senior party colleagues are understood to have advised him the best time for him to deal with that is when he returns to give evidence at the tribunal next month.Meanwhile, some senior colleagues, while continuing to publicly express support for Ahern, have been reluctant to say if they believe all his evidence so far to the tribunal.Both Defense Minister Willie O'Dea and Social Affairs Minister Martin Cullen refused to give their own views when approached by the Irish Examiner newspaper.Separately, both Enterprise Minister Micheal Martin and Agriculture Minister Mary Coughlan, a rising star in government, said it was not for them to judge if Ahern was to be believed, although both insisted they had full confidence in his ability to run the country.There was more than a hint in the Fianna Fail air that potential leadership contenders are lining up for a takeover battle whenever Ahern does decide to quit.Tanaiste (Deputy Prime Minister) Brian Cowen is firm favorite and Ahern's own choice as his successor.But others, including Coughlan and Justice Minister Brian Lenihan, indicated last weekend that they haven't ruled themselves out, although they also insisted they don't expect Ahern to quit before his intended date -- 2011, when he's 60.