The Newstalk ZB broadcaster learned of his success during a phone call with the Otago Daily Times at about 1.30pm.
Voting opened on January 26, following the resignation of former deputy mayor Toni Biddle in October.
Votes for the by-election closed at midday today, and while the results did not include special votes, Mr Lush beat other candidates by securing 7003 of the 13, 991 votes counted.
Deputy Electoral Officer Michael Morris said Mr Lush received more than half of the votes counted.
"While special votes still need to be counted, as well as any votes dropped off to our ballot boxes today, the margin between the candidates is significant enough that we are confident Mr Lush will be your next Councillor."
The candidate with the second most votes was Wayne Harpur with 1457. After him, came Simon Edwards with 1090.
In total, there were nine candidates.
It was not yet known how many votes have been cast today, being the final day of the by-election, however the return rate thus far had been 34.86 per cent of eligible voters.
Final confirmation of results, which will include special votes, will be made on Saturday.
