Candidates for the Eden-Monaro byelection rushed across the corners of the electorate from dawn till dusk on Friday, hoping to turn every last undecided voter their way as the poll was set to come down to a knife-edge.
As the final pre-poll votes were cast before voting day, the Australian Federal Police confirmed they had made an arrest related to an email campaign making false claims about the Labor candidate.
Decided by around 1600 votes last year, the ultra marginal electorate is winnable for both Labor's Kristy McBain and the Liberals Fiona Kotvojs, although preferences from the Greens, Shooters, Fishers and Farmers Party and the Nationals were set to play a role in the final outcome.
Dr Kotvojs was campaigning in the northern part of the electorate, where the government promised a $31 million upgrade to a defence facility at Bungendore on the final day of campaigning. In Jerrabomberra on Friday afternoon she greeted the steady stream of voters as they arrived to cast their votes.
Ms McBain was focusing on her home area of the far South Coast, appearing with Labor leader Anthony Albanese in Narooma and Cobargo in multiple media opportunities.
The most recent polling has Labor winning the seat 52-48, but with a 4 per cent margin of error, no party was treating the race as already run.
With less than 24 hours to go before the official voting day started, the Australian Federal Police said it had charged a 32-year-old man over "offensive and harassing" spam emails that attacked Ms McBain.
The Blacktown man was arrested during a search warrant at his house on Thursday night and later charged with one count of using a telecommunications service to menace, harass or cause offence.
Emails have been sent during the campaign falsely claiming Ms McBain had pulled out of the race due to illness and votes wouldn't be valid unless they preferenced Dr Kotvojs above Labor.
The series of emails had made a number of other claims about Ms McBain but it was the emails making false claims about the way the election was being conducted that forced the Australian Electoral Commission to take action and refer them to police.
Ms McBain said she welcomed the arrest and thanked the federal police for their work.
"It's obviously concerning that [the email campaign] potentially has an impact on [Saturday's vote]," she said.
"I think any misinformation campaigns like we have seen with the email trail have been disappointing and is not something we want to see in our democracy."
Dr Kotvojs has previously condemned the emails.
A statement from the federal police said it began an investigation following a report from the Electoral Integrity Assurance Taskforce and the Australian Electoral Commission on June 10.
"The report related to spam emails, which appeared to be from legitimate sources, being sent from an unidentified user to the Australian community and various organisations," the statement said.
"The emails were assessed as offensive and harassing in nature,
"The AFP investigation identified the use of a number of telecommunications services subscribed using suspected fraudulent identification documents. Investigators will allege in court that these activities were linked to the 32-year-old man."
The man was released on police bail and is due to appear before the Blacktown Local Court on September 2.
The AFP said an investigation into the matter remained ongoing.
The Australian Electoral Commission said it was aware of the AFP's actions.