Luke Herdegen secured a commanding position in the Secret Harbour by-election after a decisive primary vote swing of around 30 percentage points delivered One Nation its first Western Australian lower house seat. The contest followed Labor minister Paul Papalia’s July resignation, which opened a previously safe seat held on an 11.5 per cent margin in 2025. With roughly 75 per cent of votes counted on polling day, Herdegen led on first preferences at 39 per cent against Labor’s Georgia Tree at 24 per cent and the Liberal candidate at 17 per cent, translating to a two-candidate-preferred margin exceeding 14 points. Traders priced near-certainty into the outcome because the remaining early and postal votes showed no realistic path for Tree to close the gap. The only plausible challenges would involve an unprecedented reversal in final preference distributions or an unforeseen administrative delay in the official declaration, neither of which has precedent in comparable WA by-elections.