Former MP Ron Mark has re-joined New Zealand First, possibly at the expense of sitting MP Andrew Williams.
Mr Mark, who is the Mayor of Carterton, confirmed today that he would run for the Wairarapa seat.
He said his time as Mayor had been "brilliant" but he had become frustrated by the impact of central government policies.
"I've consistently had it from people in the region, who have said I can serve us better by going back to Parliament."
He served as a New Zealand First list MP between 1996 and 2008.
It is understood that Mr Williams, who is currently New Zealand First list's third-ranked MP, has fallen on a draft list to make way for Mr Mark.
Mr Mark said he had not seen any party list and would not comment.
The Wairarapa seat is vacant after the departure of National MP John Hayes. The seat includes Dannevirke and stretches up to Central Hawke's Bay.
- NZ Herald