Mick Brookes, a Nottinghamshire junior school head and past president of the National Association of Head Teachers, is to challenge David Hawker, the education director of Brighton and Hove, who was selected last week by a union sub-committee which had received advice from headhunters.
Mr Brookes has written to the union's 11 regional executives, seeking their nomination for him to succeed David Hart as general secretary in September.
If three of them vote to back him by the January 21 deadline, a figure he is confident of reaching, then a leadership election will be triggered.
Mr Brookes, NAHT president in 20001, said: "I don't think the right decision has been made. The union needs someone with recent experience of working in a school."
But the man who chaired the selection panel said it was unlikely he would get NAHT Cymru's nomination. Gareth Matthewson, the association's immediate past president and head of Whitchurch high, Cardiff, believes the right person has been selected.
"NAHT is a democratic organisation and if Mick wants to put himself forward, he can," said Mr Matthewson.
"We recommended David Hawker, following an exhaustive selection process. We were impressed with his experience and success both at the Qualifications and Curriculum Authority and at Brighton.
"We feel his experience and talents would bring a great deal to the association."
Mr Brookes applied for the post but did not make the long-list. Mr Hawker was selected by a majority of the seven-member personnel committee from three short-listed external candidates.
But a large number of national council members, who heard 20-minute presentations from all three, are understood to be unhappy at the decision.
"People were underwhelmed by the candidates we saw," said one who wished to remain anonymous. "We expected to be impressed but didn't feel that we were."
Others do not want an election. Clarissa Williams, a member of the personnel committee, is concerned it could create division. She said the committee's remit was to find someone suitable for developments such as the Children Act. Under Mr Hawker, Brighton has been one of the first authorities to create the kind of children's department it requires.