WA Labor campaign strategist Magenta Marshall has firmed as the likely replacement to Premier Mark McGowan in the ultra-safe seat of Rockingham. Mr McGowan’s unexpected departure from the seat he has held since 1996 has created an opening in one of the party’s most coveted electorates, which is currently held on a margin of 37.7 per cent. A big field of potential Labor candidates was quick to emerge last week but Ms Marshall has won the backing of the party’s Right faction and is expected to secure preselection, which is expected to formally open within days ahead of a by-election in late July. Ms Marshall, aged in her late 20s, grew up in Rockingham, lives in the electorate where she is married to a teacher and has spent most of her working life with WA Labor. That includes a stint in the electorate office of Balcatta MP David Michael, who was on Wednesday promoted to Local Government Minister, before joining party headquarters in a more specialised campaigning role. Ms Marshall coordinated Mr Michael’s re-election campaign at the 2021 State before joining Labor HQ ahead of the 2022 Federal elections, contributing to resounding wins for Labor in both instances. Her LinkedIn profile describes her as the director of local campaigns and women’s organising for WA Labor. In the past five years, WA Labor has lifted its rank-and-file female membership from 36 to 45 per cent. The party has long placed special emphasis on recruiting female members and has a gender quota of 50 per cent female representation in caucus by 2025 - a level it has already achieved. If Ms Marshall were to replace Mr McGowan, the male-female split in the Legislative Assembly would flip to 26-27 - meaning women would hold the majority of Labor’s seats, which is already the case in the Legislative Council. The party is understood to be keen on installing a young, high-calibre MP in the seat of Rockingham with the potential to emulate the longevity of Mr McGowan’s 27-year political career. Given the current stage of the electoral cycle and the size of Labor’s existing backbench, whoever wins the seat is unlikely to find themselves in Cabinet until next decade at the earliest – and possibly only after a period in opposition. Ms Marshall was approached for comment. WA Labor assistant state secretary Lauren Cayoun was also strongly considered for Rockingham but is preparing to temporarily step into the state secretary role in place of Ellie Whiteaker when the latter goes on maternity leave. Ms Cayoun running in the by-election would leave the administrative wing of the party without two of its most senior leadership figures. Former Labor state secretary Matthew Dixon – who resigned after it emerged he spent WA party funds on Bill Shorten’s ill-fated 2019 election campaign without the proper authorisation – lives in Rockingham but is understood to have never been a serious contender. United Professional Firefighters Union WA branch president Clem Chan has expressed an interest in the seat but lacks party backing. Mr McGowan’s former chief of staff Daniel Pastorelli was also considered but ruled himself out, while Mineral Resources chief people and shared services officer Bronywn Grieve was also sounded out but could not be persuaded to throw her hat in the ring. A date is yet to be set for the Rockingham by-election but it is likely to take place in late July following the school holidays. The WA Liberals have not yet decided whether they will field a candidate but is considered unlikely given the expense involved and the tiny prospect of victory.