Many of her positions are closely aligned with President Trump’s messaging. Last year, she spoke at the Conservative Political Action Conference in Mar-a-Lago, where she praised Mr. Trump’s policies and laid out her aims of wanting to mirror them in Australia.

In a victory speech on Saturday evening, she struck a Trumpian note.

“We have a plan for the future of this nation,” Ms. Hanson said at her party’s celebration, adding: “I don’t want Shariah law on our doorstep. I want true people that want to come on board to be Australians, and join us in this journey of making our country the greatest country in the world again.”

The victory of One Nation’s candidate, David Farley, an agricultural businessman, still leaves the party far from substantial power in federal government, and a full picture of its support nationwide won’t come until the next federal election, which isn’t expected until 2028. The party has one other representative in the lower house, who defected from the National Party last year, and four members, including Ms. Hanson, in the Senate, where seats are proportionally allocated based on votes cast for the party.

But the newly gained federal seat, on top of the party’s success in recent state-level elections in South Australia, where it edged out the Coalition, could give it the momentum to continue its rise, Mr. Moffitt said. It has also garnered support in recent months from deep-pocketed backers, including the mining magnate Gina Rinehart, Australia’s richest woman, who gave Ms. Hanson a private plane.

“There’s wind in their sails,” Mr. Moffitt said.

The candidate who finished second, Michelle Milthorpe, is an independent. Labor did not have a candidate in the race, and the Coalition was not a significant contender.