DUP representative Nigel Kells is stepping down from Antrim and Newtownabbey Borough Council.
Mr Kells worked as campaign manager for Emma Little-Pengelly in 2016 as she sought to retain her Stormont seat.
Once regarded as a future MLA, the departing councillor said his decision to quit had been prompted by "changes in my personal life".
Mr Kells split from his wife Desna, the mother of his three children, in 2016.
He is now engaged to Gibraltar netball player Meg Martinez.
He will remain in post until the end of September when the DUP is expected to co-opt a replacement.
