Mr Hipkins edged Prime Minister Chris Luxon in a combative and at times offbeat debate on Tuesday.
A panel of 100 undecided voters sided with Mr Hipkins, with 49 saying they had been won over by the Wellingtonian, compared with 24 for National's Mr Luxon.
That result is the latest evidence that the race to polling day on November 7 is beginning to break for Labour.
In two polls released on Tuesday from TVNZ and Radio NZ, the left bloc held a narrow edge over the National-led coalition, owing to Mr Luxon's decision to rule out working with upstart party Opportunity.
New Zealand's electoral system makes minority governments all but certain, meaning parties must cobble together coalitions through negotiations after election day.
In one of the last questions of the night, Mr Luxon was asked if he might revisit drawing a line through Opportunity.
"We've ruled them out ... we do not want to work with parties that want to impose more taxes," he said.
Central to Mr Luxon's pitch is a pledge to impose "no new taxes" on Kiwis, in contrast with Labour, which is promising a capital gains tax on investment homes and businesses.
The topic also drew his biggest hiccup of the night.
Asked if he could guarantee no existing taxes would be increased in the next term, he said yes, allowing Mr Hipkins to quickly fact-check with a National pledge to put up fuel tax, drawing a shift concession from Mr Luxon.
Quirky questions often derived the most interesting responses.
Would the candidates prefer the Warriors to win the 2017 NRL premiership or the All Blacks reclaim the World Cup?
"Up the Wahs," offered Mr Hipkins after a moment to consider, with Mr Luxon offering "go the All Blacks".
Mr Luxon said parents shouldn't be allowed to take their children on a family holiday during school term, while Mr Hipkins said only that he would prefer they didn't.
The moment that made each man the proudest to be a New Zealander?
Mr Luxon nominated meeting Kiwi soldiers in Britain who were training Ukrainian forces in their war with Russia; Mr Hipkins said New Zealand's unity following the Christchurch terror attack.
On foreign affairs, Mr Hipkins was unequivocal on a string of issues: that both Iran and US had broke international law in their ongoing war, that Israel was committing genocide, and Palestine should be recognised.
On each of those issues, Mr Luxon deferred judgment.
Mr Hipkins was strongest on cost of living responses, reeling off his party's many policies in the area, but conceded his former government was too slow to act on crime.
He also offered his counterpart praise for sealing a free trade agreement with India, a pledge made in a 2023 election debate that Mr Hipkins then derided as unachievable.
While most political analysts followed the lead of undecided voters in declaring the debate for Mr Hipkins, veteran journalist Richard Harman declared it a draw.
"(Mr Hipkins) needed a breakout and I don't think that happened ... I think it was a bit flat," he said.
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