Whangarei District Council begins a review on Monday of chief executive Mark Simpson.
He has sacked one employee for nominating a mayoral candidate - but let another work for a rival candidate.
Mr Simpson's personal assistant Jan Walters was dismissed for nominating former mayor Stan Semenoff.
But executive assistant Ford Watson says he was given permission by Mr Simpson to edit campaign material for the council's finance chairperson, Warwick Syers.
Mr Watson says the council's election protocols warn staff to remain neutral - but enable the chief executive to compromise that neutrality, by letting staff work on political campaigns at his discretion.
He won't comment on whether Mr Simpson has expressed support for Mr Syers' mayoral bid.
Other council sources say senior managers don't want Mr Semenoff back in the job.
The review is led by Auckland lawyer Simon Stokes.