Mr Ranga was the highest-polling unsuccessful council candidate in the election in October, finishing 15th in the race for 14 councillor positions.
He felt it "wasn’t my time" then and this remained the case now.
"Another opportunity has come my way and I’m probably more committed to that than I would be at running for council — and I couldn’t do both justice."
A vacancy at the council was created by the death of Cr Jules Radich and a by-election is required to replace him.
Nominations for the position open on February 2.
Several possible candidates remained on the fence yesterday about whether they would stand.
Andrew Whiley, who lost his council seat in October and finished just behind Mr Ranga, said he was considering running again.
Carmen Houlahan, another councillor who was not re-elected last year, declined to comment.
Jett Groshinski, who was endorsed by the Labour Party for the previous campaign, said he was yet to decide.
The by-election could cost the council about $400,000.
Cr Russell Lund and Otago Peninsula Community Board chairman Paul Pope were two people who questioned whether a by-election was necessary in the circumstances, as Mr Radich died within three months of the election.
They wondered if the government should change the rules for such scenarios in future.
Mr Whiley indicated he would have been comfortable with the highest-polling unsuccessful candidate from October being invited to serve, but the fact was a by-election had to be held — legislation required it.
University of Otago law professor Andrew Geddis said a new election had to be held to determine which of the "still-willing candidates" had the most support from voters.
"Even if only a short time has elapsed since the last election, things may have changed considerably," Prof Geddis said.
The next cab off the rank may have moved on, he pointed out just before the Otago Daily Times established this was in fact the case with Mr Ranga.
"New people, having seen who has been elected, may decide that they wish to be candidates," Prof Geddis said.
"Voters may want to change voting decisions made even a short time earlier.
"In short, you can’t fish in the same river twice, as circumstances and conditions are always changing."
Prof Geddis highlighted the single transferable vote electoral system would again be used, "which may require voters to examine the claims of a considerable number of candidates in order to rank their preferences for the one position that is up for election".
