Sophie Mirabella, a close colleague of Tony Abbott and one of Australia's most abrasive politicians, looks almost certain to be the Coalition's highest-profile election casualty, thanks to the unexpected popularity of a little-known independent challenger.

Mirabella quit Abbott's front bench yesterday, after the discovery of more than 1000 misplaced ballots gave Cathy McGowan a near-unassailable lead of 1152 votes in the northern Victorian seat of Indi. The 44-year-old, set to be industry minister, ruled herself out of Cabinet contention, saying "my own future in Parliament is not assured".

McGowan, 58, a sheep farmer and rural consultant with deep roots in the safe Liberal territory of Indi, told the ABC Mirabella - who had a 9 per cent majority - had taken locals for granted.

Mirabella's political foes, and even some members of her own party, have been watching with glee. A former lawyer, the MP was one of five Liberals who absented themselves from Parliament for Kevin Rudd's apology to the Stolen Generations.


She likened Julia Gillard to Colonel Muammar Gadaffi in 2011, saying both were "delusional", and poked fun at Gillard's childlessness. She also called for Muslim girls to be banned from wearing headscarves at school. The retiring independent MP, Tony Windsor, known for his generosity of spirit, recently called Mirabella the "nastiest" person in politics, and the person he would miss least.

Now she looks likely to be out of a job, thanks to her challenger's grassroots campaign. McGowan, who was active in the group Rural Australians for Refugees, recruited 500 volunteers. Younger members of her large family ran her social media campaign.

McGowan said yesterday that while she was not claiming victory, with some postal and absentee votes yet to be counted, "the level of optimism has certainly increased in [our] camp".

Mirabella, who shot to prominence as an outspoken monarchist in the run-up to the 1999 referendum on an Australian republic, is seen as part of the social-conservative right. A shadow frontbencher since 2009, she believes in tax cuts and reduced government spending.

In 2005, she accused four Liberal MPs who criticised the mandatory detention of asylum-seekers of behaving like "political terrorists".

She told veteran Liberal senator Bill Heffernan to "go and pop your Alzheimer's pills", and called Malcolm Fraser, the former Liberal Prime Minister, a "frothing-at-the-mouth leftie" for questioning the 'war on terror'.

She is loathed by the family of her former partner, Colin Howard, a law professor who died in 2011. He left her his entire estate and reportedly also gave her more than A$100,000 to help her get elected in 2001.

Now married to Colin Mirabella, a former Australian Reserve officer, she has two daughters. In 2008, when she was heavily pregnant with her first child, the then Labor MP Belinda Neal - no slouch herself in the insults stakes - told her: "Your baby will be turned into a demon by evil thoughts."