(CNN)The man bidding to be Australia's next leader is a 52-year-old former unionist and ardent republican known for both his love of dad jokes and his "assassin" role in bringing down two sitting Prime Ministers.
Six things to know about Australia's leadership hopeful Bill Shorten
As Australians vote on Saturday, polls indicate that Bill Shorten, leader of the center-left Labor Party, is likely to be the country's 31st Prime Minister.
Shorten is up against incumbent Scott Morrison, the leader of the center-right Liberal Party, who has held the top post for less than a year.
If Shorten wins, he'll be Australia's sixth leader in a decade marred by party infighting and leadership coups.
Shorten, who is credited with bringing unity to the Labor party, has been campaigning under the slogan of "A fair go for Australia," his second attempt at becoming Prime Minister.
Although he's been Labor leader for almost six years -- the party's longest-serving leader in almost two decades -- he remains a relative unknown on the international scene.
Here are six things you need to know:
Although Shorten joined the Labor party at 17, he cut his teeth in union politics. In 1994, he joined the Australian Workers' Union, straight out of studying law at Monash University in Melbourne, and worked for similar organizations for the next 23 years until he was elected to parliament.
"Bill was able to recruit, represent people and organize," former Australian Council of Trade Unions head Bill Kelty told Australian publication The Monthly.
"He was able to have a fight, but he was also able to compromise and negotiate, not out of weakness but out of strength, and have a good relationship with business leaders."
Shorten first came to national fame in 2006 when the Beaconsfield Mine in Tasmania collapsed and trapped two workers. He became the public face of the incident, liaising with and supporting the family and community.
As a powerful member of Labor's right-wing faction, Shorten was closely involved in replacing then-Prime Minister Kevin Rudd in June 2010 and crowning Australia's first and only female leader, Julia Gillard.
He quickly gained a reputation for being a behind-the-scenes power broker, and the image was reinforced when he publicly supported Rudd's bid to remove Gillard three years later.
A poll conducted after he took over the Labor leadership at the end of 2013 showed just 34% of Australians considered him "trustworthy."
Shorten is promising to crack down on tax loopholes used by multinational companies, introduce tax cuts for low and middle-income Australians, and make large companies reveal their gender pay gaps.
He's also promising "real action" on climate change -- a contrast with the Liberal party, which has several prominent members who are climate change skeptics.
Under Shorten, Labor says it will create clean transport infrastructure, invest in renewable energy and aim to reduce pollution by 45% on 2005 levels by 2030.
"I just don't want my children to come and see flora and fauna, I want their children to come and see it, and future generations to see what makes Australia so special," Shorten said earlier this month after holding a koala on the campaign trail.
Australia's head of state is still the UK's Queen Elizabeth II -- but that could change under Shorten.
Shorten has previously promised to hold a plebiscite to gauge support for Australia becoming a republic with its own head of state. That would then be followed by a formal referendum. Becoming a republic is on Labor's policy books.
"We can vote for a republic and still binge-watch 'The Crown' on Netflix," Shorten said in 2017. "And we can vote for a republic without derailing the business of government, or the priorities of this nation."
Shorten has consistently ranked poorly in preferred Prime Minister polls. Australian media has described him as unlikeable. But two women have helped humanize Shorten this campaign: his wife and his late mother.
Shorten's wife Chloe -- a former journalist turned media consultant -- has been described as a "campaign-trail asset."
While Shorten has struggled to inspire voters, his wife has been called "warm" when accompanying him on the trail. If Shorten becomes Prime Minister, she has said she wants to use her platform to promote feminist causes.
"I think that I will always bang on about the things that are very unjust for women because they are still there," she told site Future Women.