According to the Election Commission of New Zealand, Ardern's Labour Party are on 49% of the vote, while the National Party are expected to win 27% with the ACT New Zealand and Green parties both on 8%.
If Labour wins more than half the seats, Ardern could form the first single-party government under the current system.
The 40-year-old won a second term in office on Saturday in an election landslide of historic proportions.
A year ago she won praise for her handling of the worst terrorist attack in New Zealand's history, the Christchurch mosques shooting.
"This has not been an ordinary election, and it's not an ordinary time", she said.
"The bottom line is I believe he's going to do a lot better than people think he's going to do", he said. National will reemerge from this loss a stronger, more disciplined and more connected party.
Although the title referred to New Zealand's lack of constitutional constraints on governments and their leaders in general, it was given added pointedness by the willingness of Prime Minister Rob Muldoon to push the boundaries of the few conventions that constrained his power. Foreign fans often compare her favorably to Donald Trump, saying the Kiwi prime minister is antithetical to everything they dislike about the United States president. These include the Christchurch mosques shootings in March past year, when a white supremacist gunman killed 51 Muslim worshippers, and a volcanic eruption that claimed 21 lives last December on White Island, also known as Whakaari.
John Legend pays tribute to 'humbling' Chrissy Teigen following baby loss
The crooner took the stage at the Dolby Theatre in Los Angeles to deliver a touching performance of his ballad, " Never Break ". At the time, Legend, shared Chrissy's public statement, adding, "We love you, Jack ", which was to be the baby's name.
Ms Ardern also told the people of New Zealand the Labour party would "not take your support for granted". She shut the borders and outlined an ambitious goal of eliminating the virus entirely rather than just trying to control its spread.
In the battle against Covid, Ardern was alone among her western peers in pursuing an explicit elimination strategy and imposed one of the strictest nationwide lockdowns in the world. After more than 100 days without community transmission, an outbreak flared in largest city Auckland, but that was also quickly stamped out. The only new cases found recently have been among returning travelers, who are in quarantine.
Results of the referendums will be announced on October 30.
The Auckland outbreak also prompted Ardern to postpone the election by a month and helped increase the early voter turnout.
While the count has not been finalized, the figures were enough for opposition leader Judith Collins to concede after phoning Ardern. Collins, 61, is promising sweeping tax cuts in response to the economic downturn caused by the virus.
Labour was seeking a second term on the back of Ms Ardern's success in containing coronavirus, while Ms Collins argued she was best placed tackle the post-pandemic financial challenges. Collins, who took over the National Party in July after a period of turmoil when the party had three leaders in three months, said the false start had cost her campaign momentum.
Not only has that never happened under MMP, but you have to go back to 1951 to find a party that got more than 50 per cent of the popular vote.