Pat Farmer has completed dozens of ultramarathons in his lifetime.
They have included journeys across the Americas and several trips around Australia.
But the 61-year-old said none have felt as important as his latest challenge, running more than 14,000 kilometres across Australia to promote the upcoming Voice to Parliament referendum.
"We've got one chance in a lifetime, in my lifetime, to be able to vote yes," he said.
"The time is now and for that reason, I'm incredibly motivated to push myself day in, day out until the job is done."
The former federal Liberal politician currently lives at Copacabana on the New South Wales Central Coast.
He passed through his home town this week, but did not stop for a night's rest in his own bed.
"I need to stay on the road until the job is done," he said.
"I still have another 4,500 kilometres of this journey to do."
From Tasmania to Uluru
Mr Farmer started the run in Tasmania in April and made his way past the Sydney Opera House on Tuesday, where he was joined by Prime Minister Anthony Albanese.
"[It's] an extraordinary effort," Mr Albanese said.
"Pat Farmer and his team have been raising awareness and talking to people about what this referendum is about."
The ultramarathoner will continue through to Canberra, Melbourne, and Adelaide before making his way up to the "spiritual heart of Australia", Uluru.
He will continue to run between 65 and 80 kilometres each day, with the aim of reaching Uluru in October.
His stamina still impresses his daughter, Brooke, who has grown up watching her dad run for a variety of different causes.
"It's really impressive and mind-boggling," she said.
"[This run] does feel very different and hopefully what he's doing will make a difference and have a positive impact on people."
Mr Farmer said there had been a mixed response from people he had met across the country.
"You're going to get varying points of view," he said.
"But overwhelmingly the support for the Yes campaign around the country, from what I have seen, is to say yes."
10 pairs of shoes down, five to go
During the past three months, Mr Farmer's shoes have hit melting bitumen, bright red dust, and sandy roads.
He has already worn through 10 pairs in that time.
"I usually go through about one pair of shoes for every 1,000 kilometres that I cover," Mr Farmer said.
"I have 30 pairs of shoes, but I'll probably use around 15 pairs in total.
"It's very, very difficult to stay mentally focused on this role.
"[But] the one thing that's keeping me going is the purpose."
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