But while using media interviews to back Alun Michael, he steered well clear of an endorsement at a potentially troublesome question-and-answer session with Labour activities.
Tony Blair said: "I make no apology for supporting Alun Michael; I think he's a great guy. That's why I've appointed him to the job. I put my seal on him the day I appointed him Secretary of State for Wales.
When addressing Labour luminaries, however, Mr Blair emphasised that the choice of First Secretary for Wales lay with Welsh party members, not with Labour's London headquarters. "There will be no support from Millbank for any one candidate," he said.
His magisterial comments yielded praise from Rhodri Morgan, the man that the Prime Minister wants to withdraw from the battle. Mr Morgan said Mr Blair had behaved with "studied neutrality".
That belied the political significance of the prime ministerial day trip to Wales which clearly identified Mr Michael as the "official" candidate. The favoured son, however, has a fight on his hands.
Mr Morgan confirmed his determination to stand for office and clearly enjoys considerable grass roots support. He has a reputation as a maverick, but made a name for himself as chairman of the Public Administration Committee which recently carpeted Alistair Campbell, the press Secretary at No 10.
Mr Michael is regarded by Downing Street as a "safe pair of hands" and the prime minister yesterday repeatedly stressed the need for stability and continuity.
He told the Q & A session at the University of Glamorgan, Pontypridd, that accusations Mr Michael had been "parachuted in" were media-inspired. Any idea there was some kind of split between London and Wales was "piffle". To cheers, he added: "Don't let the media ruin this election for you."
He concluded: "As leader of the Labour Party I believe it would be the beginning of the end for us if we thought in terms of England versus Wales or England versus Scotland. I am proud that we are part of one Labour Party."
While most of the activists at the meeting were hand-picked Blair supporters, a few dissidents escaped the selectors. One asked why the Government was not redistributing wealth from the rich to the poor; another urged him to ensure that proposals for union rights were not watered down.
Mr Blair clearly impressed most of the audience. Angharad Davies, who contested Montgomery in the last election, said: "He was very coherent and got it absolutely right."
Earlier, Mr Blair drove to Abercynon, a valleys town still suffering from the closure of Penrhiwceiber Colliery in 1985.Reuse content