Winston Peters has won the Northland by-election, ahead of his nearest rival by nearly 4,000 votes.
In his victory speech, Mr Peters told his crowd of supporters that differences must now be put aside.
"We are under no illusion of the massive job we have ahead of us, we must restore this province's rightful position in New Zealand."
With 100% of the votes counted, the New Zealand First leader has 15,359 votes.
National candidate Mark Osborne secured 11,347 votes followed by Labour's Willow-Jean Prime with 1,315.
Mr Osborne's campaign manager Steven Joyce says Northlanders voted for Mr Peters because of a case of "better the devil you know".
He said Mr Osborne ran an outstanding campaign and hoped he had a future with the National Party.
The Northland seat is vacant after the resignation of National's Mike Sabin.
"Tonight we must thank the people of Northland who put their party aside and came out for Northland" - Peters pic.twitter.com/RqOEW2lPmx— Katie Bradford (@katieabradford) March 28, 2015
Mark Osborne arrived at his event in Kerikeri to a huge applause and conceded defeat.
He admitted he's lost by a significant margin and said it had been a tough day.
Ron Mark and Tracy Martin hug. The celebrations at the Duke begin. No Winston yet. pic.twitter.com/8RvnOUoXWU— Katie Bradford (@katieabradford) March 28, 2015
With more than 99% of the votes counted, Winston Peters has won by a majority of 3,995 votes.
Winston Peters is leading by 3,888 votes and is on track for a historic win.
Support is flowing for Winston Peters on the ONE News Facebook page tonight.
With 90% of the votes counted, Winston Peters leads by 3,513 votes.
Shane Jones, Dover Samuels and Pita Paraone. All very happy tonight. pic.twitter.com/9VZNwRfXg1— Katie Bradford (@katieabradford) March 28, 2015
With National Party supporters still waiting on candidate Mark Osborne pic.twitter.com/tJceyIKWPM— helen castles TVNZ (@helencastles) March 28, 2015
People have started arriving at Winston Peters' by-election night event as he starts the night with a commanding lead over nearest rival Mark Osborne.
Former Labour MP Dover Samuels is there to support Mr Peters and his old mate Shame Jones is also expected to turn up.
More than 70% votes counted in the Northland by-election. Winston Peters leading the charge.
Steven Joyce shows his support for National candidate Mark Osborne in Kerikeri. He arrived with Paula Bennett but Mark Osborne is yet to show up.
The drinks are flowing and the atmosphere in general is lively but more serious at the Bennett and Joyce table.
One News Political Reporter Katie Bradford is on the ground in Russell.
Live entertainment outside the Duke of Marlborough pic.twitter.com/Roi5TQrXRD— Katie Bradford (@katieabradford) March 28, 2015
Andrew Little congratulates Labour candidate Willow Jean-Prime.
Early Northland by-election results meeting predictions. Very proud of Willow Jean Prime's campaign. A force for the future for the North— Andrew Little (@AndrewLittleMP) March 28, 2015
Yesterday's ONE News/Colmar Brunton poll showed Mr Peters way ahead with 53% support, while Mr Osborne lagged behind on just 36%.
Join us throughout the night for updates and political analysis from the ONE News team.
Winston Peters now 1500 votes ahead. 16% counted.— Katie Bradford (@katieabradford) March 28, 2015
Earlier this month Mr Osborne, National's candidate, revealed plans to spend up to $70 million upgrading bridges on state highways in the region over the next six years but many viewed the announcement as nothing more than a by-election bribe.
Mr Peters' lead is largely due to the backing of Labour voters, after party leader Andrew Little hinted they should back Mr Peters instead of Labour candidate Willow Jean-Prime.
Who do you think is going to win? Join the conversation on the ONE News Facebook page.