Labor's Maryanne Stuart will take on Heathcote MP Lee Evans for the third state election in a row.
Ms Stuart won the preselection vote on Saturday, defeating Sutherland Sutherland Shire councillor Diedree Steinwall 74 votes to 21.
"We were all really grateful to have a rank and file preselection because it's allowed members in the Heathcote Labor party branches to have their say and to be able to choose the candidate of their choice," Ms Stuart said.
With the recent electoral redistribution turning Heathcote into a notional Labor seat with a 1.7 per cent margin, party insiders have said it is one of the two Illawarra and Shoalhaven seats the party is targeting.
The other is the Liberal-held seat of South Coast.
Having run against Mr Evans twice before, Ms Stuart believed her "face and name recognition" will help her chances, along with the fact that she had continued to work with the community "like a quasi-state MP".
A full-time campaigner with the Australian Conservation Foundation, Ms Stuart has taken leave to contest the March 2023 election.
The redistribution has added the suburbs between Thirroul and Coledale into the electorate, which creates a seat split between the Illawarra and southern Sydney.
Ms Stuart said that made for a diverse range of communities.
"There are similarities of issues across the seat but there are also completely different communities," she said.
"There's Woronora River to Sutherland over to Bundeena, then Helensburgh and all the way down to Bulli. So there are different communities, there are different local issues. But there are also common issues across the electorate and those that are state so there's a three-level campaigning strategy."