The 60-year-old man was allegedly attacked with a baseball bat at his home on Scorpio Street in Torquay, south west of Melbourne, about 7.45pm on Sunday.
Police responded and arrested two people - a 14-year-old boy from the Casey area and a 37-year-old man from Hampton Park.
The older man was charged with intentionally cause injury and other assault-related offences and remanded to reappear at Geelong Magistrates' Court on November 10.
The 14-year-old boy was issued with a caution.
The alleged victim was taken to hospital with non-life-threatening injuries.
The party reported the incident to media on Tuesday, with One Nation Victoria leader Warren Pickering labelling it "un-Australian."
"Political violence or intimidation of any kind against anyone is unacceptable in this country," he said.
"It you don't like someone's politics, you vote accordingly. You don't assault them."
Mr Pickering said all people and parties contesting the Victorian election should uphold democratic principles and engage in honest but peaceful debate.
"I understand this is a critical election without recent precedents. I understand many Victorians are frustrated. I understand the 'temperature' of debate is high," he said.
"We don't have to accept the erosion of the middle ground for respectful debate or peaceful disagreement.
"We must build that ground up and give it unassailable foundations."
It comes as the Victorian state election period officially got under way on Tuesday, with the signing of writs by Governor Margaret Gardner, formally calling an election.
The writs will be delivered to the electoral commissioner, formally dissolving the state's 60th parliament and officially setting a date for the election as November 28.
The writs also stipulate a time from which the electoral roll will be closed and no new enrolments accepted.
Victorians still have until 8pm on Tuesday to make sure they're enrolled.
Once the writs are signed and issued, candidates can officially nominate for election and have until midday on November 9 to do so.
From 6pm on Tuesday, the government will enter what is known as "caretaker mode", during which it will avoid implementing significant policy actions while continuing with the administrative running of the state.
After the results of the election are declared the writs will be returned to the governor of Victoria with the names of the elected candidates in both houses of parliament.
Campaigning has already been under way for weeks, in what has been labelled one of the most consequential elections in recent history.
One Nation is polling nearly as strong as Labor in the primary vote, according to some polls, enjoying heightened popularity and a chance of claiming multiple seats.
A Roy Morgan poll published on Friday showed One Nation polling at 22 per cent, behind Labor's 22.5 per cent.
According to the Roy Morgan poll, the coalition held a commanding grip with 29.5 per cent of the primary vote and the best chance of forming a majority government.
The election will be a major test for Labor, which is seeking a fourth consecutive term after 12 years in government and with baggage dating from well before COVID-19 battered the state.
The Greens, which have largely failed to capitalise on disillusioned Labor voters, were polling 1.5 per cent lower at 12.5 per cent of the primary vote.
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