Debates over poverty and homelessness favoured left-leaning candidates in the local body elections, says politics lecturer Bryce Edwards.
Sitting Labour MP Phil Goff won the Auckland mayoralty with a large majority, Wellington's new mayor Justin Lester ran on a Labour Party ticket and Lianne Dalziel, a former Labour MP, has been re-elected Christchurch's mayor.
"The country's looking a bit redder today in terms of political colours - candidates that are a bit more left-leaning," said University of Otago lecturer in politics Bryce Edwards.
Look back at RNZ's live coverage of all the local election action as it happened
The social and economic issues that were being debated in national and local politics - such as childhood poverty and homelessness - are beneficial to left wing candidates and parties, he said.
"And we have seen that this weekend at the election that the social issues are doing well for the more left-wing candidates."
Labour Party leader Andrew Little said the Auckland, Wellington and Christchurch mayors were elected on core Labour Party issues like housing, low wages, and inequality.
That gave the party a springboard to go into next year's general election but the "nobody can rest on their laurels".
"But I think it's encouraging to see the results that have been achieved."
Dr Edwards agreed the seemingly increased openness to progressive or left-wing candidates may not translate into votes Labour at next year's election
"You can never take too much from local body elections because they are quite different from the parliamentary general elections and this doesn't necessarily mean that National's in trouble - but Labour will be celebrating these wins."
The National Party will start gearing up next week for the by-election in Mt Roskill, held by Phil Goff for 30 years.
Mr Goff will resign in the next few days and a by-election will be held before Christmas.
National Party president Peter Goodfellow said it will begin the process of selecting a candidate next week, and though it would be difficult to win - as no government has ever won a by-election from the opposition - Labour had been taking the seat for granted.
Dr Edwards said there was a chance National could end up winning that seat.
"It's traditionally a safe Labour seat, but the demographics are changing in that area and it means there is a possibility National could win that.
"Labour could lose this and it would be a vote of no-confidence in Andrew Little's leadership and the way that the Labour Party is going at the moment."