Mr Michael, Tony Blair's choice for the post, won 60 per cent of the vote at a union delegate conference in Swansea, with his rival Rhodri Morgan, MP for Cardiff West, taking 40 per cent.
The AEEU controls 6.2 per cent of the total vote of an electoral college in which the unions, party members and MPs each have one-third of the total.
As well as boosting Mr Michael's chances, the engineers' decision will be greeted with relief in Downing Street. Mr Morgan is strongly supported at the grass roots and the party's 25,000 Welsh members are expected to vote heavily in his favour in a one-member-one-vote ballot. MPs are likely to be more evenly divided and the outcome will probably rest on the decisions of the trade unions.
Unison will next week ballot its members. Another powerful union, the GMB, will cast its block vote following "consultations" with branches. George Wright, Welsh Secretary of the influential Transport and General Workers' Union, has ruled out a membership vote on the grounds of expense.
Whoever is declared the winner on 20 February effectively becomes "prime minister" of Wales provided Labour wins a majority on the 60-seat Assembly, to be elected on 6 May.Reuse content