After the 2013 election, Liberal senator Eric Abetz got a letter from the electoral commission asking why he didn't vote.
"Luckily the media got a photo of me casting my vote and it turned out they had recorded my son as having voted twice," he said.
The veteran Tasmanian politician isn't forecasting any such mix-ups this time but admits he's still nervous about the outcome of Saturday's poll.
"I'm nervous about the result (but) hopeful that we will win," Senator Abetz told AAP on Saturday at a polling booth near Hobart.
"I did detect a bit of a swing back toward us in the last week of the campaign as people did see through the Medi-scare campaign that did bite for a while and I just hope that sufficient of our fellow Australians understand the big lie that it was."
Senator Abetz lost his cabinet spot and role as government leader in the upper house when Malcolm Turnbull took the prime ministership but has maintained the No.1 spot on the Tasmanian Liberal ticket.
"What's going to happen with the quotas is going to be anybody's guess," he said of the state's upper house result.
"The support for the Jacqui Lambie network is potentially overstated but let's wait and see."
Labor senator Lisa Singh is relying on votes below the line to retain her spot after being relegated to the widely considered un-winnable sixth spot on the party's ticket.
"It will be interesting to see if Lisa Singh's campaign takes votes away from the Greens - it's all very difficult to predict."
The senator forecast that it could take up to three weeks to finalise the upper house seats if the count is close.
"I would imagine it will take at least until the end of this month to determine the outcome," he added.
