The battle for the seat of Higgins spilled into violence with police investigating the alleged biting of a Greens volunteer by a backer of Assistant Treasurer Kelly O'Dwyer. 
Investigators have been told a 48-year-old woman was sitting in a car with a friend outside Armadale Public School on Densham Road about 9pm on Friday when two men - aged in their 60s - approached her vehicle.
The men allegedly made comments about election material for the hotly contested seat of Higgins, where a "green army" of volunteers spent the night capturing the best spots for election posters, before the woman attempted to take their photo. A Victoria Police spokeswoman said a struggle took place, and the Greens volunteer was allegedly bitten, before the two unknown men drove off in a white SUV.
Police say the woman suffered "soreness to her thumb" following the incident.
Stonnington Greens branch co-treasurer Michael McCormack, a witness to the incident, said he and the alleged victim had been left in shock by the altercation with the two suspected Liberal supporters.
"Two men approached us in the car, upset the Greens had put posters and other things up - we're talking the heartland of Liberaldom here," he said.
"I wound down the window and they got aggressive. We had been advised that if we felt threatened by people we should take their photo. My fellow Green took out her phone to do that and the guy reached across me and grabbed her and was trying to pull her phone away."
Mr McCormack said a tussle ensued as she was pulled by the arm. When the man finally let his alleged victim go and stepped away, she realised she had been bitten on the hand.
"We were both pretty shaken, we quickly called the police and went down to Prahran police station and made a statement."
Mr McCormack said in the time it took to visit the police station about half of the Greens posters were ripped down. No arrests have been made and the investigation remains ongoing.
A spokeswoman for Ms O'Dwyer denied the incident took place.
"The claims are completely false."
The Greens army of volunteers also spent Friday night swooping on the prime real estate near polling booths in other battleground seats such as Batman, Wills and Melbourne Ports. The party faithful braved the overnight chill to keep the posters up and safe.
The "greenwash" caught the two major parties napping and triggered a number of other incidents - of vandalism and posters being torn down.
Volunteer Lily King and a friend spent the night camped out in a station wagon outside Brunswick South West Primary School to keep an eye on posters left up around the school.
"There are lots and lots of Greens posters all around; we had a team get them there really early and then we took over for the night shift," she said.
"We spent the night under a doona and with a Thermos. There were a few visitors and a few people driving past and slowing down but we didn't have any problems."
Greens senator for Victoria Janet Rice said this election marked the biggest volunteer effort the Greens have ever recorded.
"They see there is such an opportunity for us at this election to be getting Greens elected," she said.