Luke Herdegen celebrates after his party claimed victory in the Secret Harbour by-election. (ABC News: Keane Bourke)
One Nation has scored a historic win in Western Australia, securing its first lower house seat in the state.
The ABC's chief elections and data analyst Casey Briggs called the outer suburban seat of Secret Harbour for One Nation's Luke Herdegen a little over four hours after votes began to be counted.
One Nation's WA leader Rod Caddies claimed victory at 9:30pm local time, although Labor had yet to concede.
Luke Herdegen will be the next MLA for Secret Harbour. (ABC News: Keane Bourke)
Labor's candidate was political staffer-turned-Woodside lobbyist Georgia Tree.
The area was traditionally safe Labor territory, having been held in different shapes and under different names since 1989, including most recently by Paul Papalia on an 11.5 per cent margin.
WA Labor Premier Roger Cook had repeatedly described the by-election as a "fight for our lives", given the threat posed by One Nation.
That the minor party was able to achieve such a large swing in Labor heartland will be watched closely around the country, both as an indication of the support behind One Nation and to learn lessons in how it can be campaigned against.
Mr Herdegen said his victory sent a loud message.
"There are no safe Labor seats in this state or in this country anymore," he said.
"A message that will send shock waves across the entire country … and put every MP in this entire country on notice.
"None of these MPs are safe from the orange tsunami."
Mr Caddies said Australia's two-party political system was "dead".
Rod Caddies (left) says most people thought a One Nation win was impossible. (ABC News: Keane Bourke)
