Labor's hopes of ending the Barnett Government after one term have taken a body blow in the once-safe seat of Kwinana.
The seat, held by Deputy Opposition Leader Roger Cook, has become marginal overnight, courtesy of an enemy from the past.
Popular local mayor Carol Adams has confirmed to The West Australian she will run again as an independent against Mr Cook, who pipped her by just 300 votes in 2008.
The 51-year-old, who all but declared victory in the last election before a late surge to Mr Cook, said she had "unfinished business".
Ms Adams was a member of the Labor Party for four years until she quit and turned independent when it preselected Mr Cook over her.
Her renewed tilt puts a different complexion on the daunting task facing Labor, which aims to hold all its 26 seats and win four others to take government.
With Ms Adams out of the picture, Labor could chalk Kwinana in the "win" column for the State election in March.
Mr Cook has a notional margin of 16.4 per cent but Ms Adams said yesterday her return slashed that to 0.08 per cent, making Kwinana one of WA's most marginal seats.
Despite conceding the previous election result was "tough", she hoped it would again go down to the wire.
"I hope it's close because it keeps the spotlight on the electorate if it is close," she said. "Certainly I see myself as the underdog. I don't have the backing financially and the support of a major political party but I'm certainly up for the fight."
Ms Adams benefited in 2008 when the Liberals, Greens and other independents gave her their preferences. She did not know whether they would again.
Despite her former Labor leanings and the fact her husband Chris Oughton has the unwinnable sixth spot on the Liberal Party's WA Senate ticket, Ms Adams insisted she was a "true independent".
The seat of Kwinana - created at the last poll from sections of Cockburn, Rockingham and the former Peel division - is bigger than the city council area but the mayor of six years said she was connecting with the wider electorate.
Mr Cook said he expected a tough contest but his incumbency and increased profile since 2008 made him confident.
"I've got a strong relationship with the electorate and obviously that's been strengthened by being the member of Parliament for the last four years and deputy leader of the party," he said.
Mr Cook said Greens voters should consider Ms Adams' connections to the Liberal Party through her husband.
WA Greens co-convener Kim Dravnieks said it was too early to say which candidates it would give preference to.