Tim Picton, who helped the party to a landslide election win, was found unconscious outside a licensed premises in Perth about 5.30am on Saturday after Western Australian police received reports of a disturbance.
His family is by his side as he remains in Royal Perth Hospital in a critical condition with serious injuries following the incident.
The 36-year-old fell after being assaulted, striking his head on the pavement, police said, adding several bystanders rushed to his aid.
"This incident is a stark reminder that split second acts of violence can have devastating, life-changing consequences," WA Police Assistant Commissioner Martin Haime told reporters on Sunday.
"The community is absolutely tired of seeing this level of violence."
Mr Martin said police were only "a matter of metres away" and arrested a 20-year-old man from Lesmurdie.
He has been charged with one count of grievous bodily harm and appeared before Perth Magistrates Court on Sunday.
Mr Picton's family thanked medical staff and police for their professionalism and support, as well as his friends and colleagues for their compassion during the "incredibly difficult time".
"As a family, we are focused entirely on being with him and supporting one another," the family said in a statement.
"Tim is a much loved father, husband, brother and son, as well as a friend to so many across Australia."
The former political strategist played an instrumental role in guiding WA Labor to their landslide 2021 election victory, in which the opposition Liberal party was left with just two seats.
He is also the brother of South Australian Health Minister Chris Picton.
Western Australia Premier Roger Cook and South Australian Premier Peter Malinauskas said their thoughts were with Mr Picton and his family.
"The whole Labor team are thinking of him and his family during this difficult time," Mr Cook wrote on social media platform X.
"It's hard to know, at these early stages, exactly what's happened to Mr Picton's brother, but he is unwell and in a serious condition," Mr Malinauskas said.
"My thoughts are with Mr Picton and Chris, and his beautiful family."
Tim Picton worked as an advisor for Senator Don Farrell in the Gillard government, then in the office of former Victorian premier Daniel Andrews before directing WA Labor's 2021 campaign.
He has since taken up a role as strategy director for mining company Mineral Resources.
24°C