Saskatchewan Party candidate Jim Lemaigre has won the byelection in the riding of Athabasca, in a stunning upset that saw him come from behind to claim victory and end a nearly 25-year NDP hold on the seat.

Lemaigre, a former RCMP officer, defeated NDP challenger Georgina Jolibois, a former five-term mayor of La Loche and NDP MP, by a margin of 11 per cent.

He took slightly more than 51 per cent of the total vote with 1,146 votes. Jolibois finished with 900 votes.

Independent candidate Darwin Roy — who lost the NDP nomination to Jolibois for the byelection — came in third with 157 votes. Last place went to Buffalo Party candidate Clint Arnason who received 12 votes.

More than 24 per cent of registered voters cast ballots in advance polls, day-of polls and at personal care facilities. Forty mail-in kits had been sent out by Elections Saskatchewan, which will be counted on Thursday. All ballot boxes are reporting but a final count will be completed Feb. 28.

Jolibois had been leading by a margin of at least 20 per cent throughout much of the evening. But as the last ballot boxes came in — mostly from bigger communities — Lemaigre pulled ahead to win.

The riding has only ever had representatives from the Liberal, Co-operative Commonwealth Federation, or New Democratic parties in its nearly 114 year history. It has been an NDP-held seat since a 1998 byelection, which saw long-time MLA Buckley Belanger switch from the Liberals to run for the NDP.

This year's byelection was called in January after Belanger resigned last August. He ran unsuccessfully as a Liberal candidate in the federal election in the riding of Desnethé—Missinippi—Churchill River.

Belanger was the longest-serving MLA in the province when he resigned.

In an interview with CBC Tuesday night, Lemaigre said he watched the results come in with his family at his mother's home on the Clearwater River Dene Nation, about 600 kilometres northwest of Saskatoon.

"At points it was kind of nerve-wracking, but I had faith in the people of Athabasca constituency and ... my success is credited to them" he said.

Lemaigre said the respect he brought to the communities he visited and listening to constituents helped him win the seat.

"One elder put it quite nicely, he said 'We've been on the outside of government for so long, why wouldn't we put ourselves back there with this opportunity,' " said Lemaigre.

Lemaigre said he has a long list of people to call and thank — including his competitors — but will be going to work right after to bring voters' concerns to Regina.

"I think the people spoke tonight and I'm really excited to represent them."

Premier Scott Moe sent congratulations to Lemaigre via Twitter late Tuesday.

"Jim will be an outstanding representative and a strong voice for the north in our Saskatchewan Party government," Moe wrote.

A spokesperson for Jolibois said she would provide comment on Wednesday.