And on Friday afternoon, the man from Te Aroha emerged the victor.
He is the 13th leader of the National Party and is the man who – bar another untimely leadership spill – will face off against Prime Minister Jacinda Ardern in the 2020 election in 120 days' time.
But for anyone following closely, Muller's rise to the political top would not have been all that unexpected.
He's been fascinated by politics since a young age.
When he was 10, he wrote a "book" in which as a young man in his 20s, he was elected Vice President of the United States, before becoming President after the Commander-in-Chief met an untimely death.
In the book, President Muller served 13 consecutive terms before dying of old age.
He still has a copy of the book, hidden away somewhere in his mother's attic.
As Muller got older, his eyes moved from the White House to the Beehive.
Leadership challenger Todd Muller (right) heads to caucus. Photo / Pool
He worked in the office of then-Prime Minister Jim Bolger in the early to mid-1990s. Muller was his executive assistant during his second term, when Bolger was rolled by Jenny Shipley.
In his maiden speech in 2014, Muller thanked Bolger for his support.
"Jim, I have always been extremely grateful for your support, now spanning across two decades."
And it looks like Muller's loyalty has paid off. Earlier this week, Bolger publicly backed his former executive assistant for the role as National leader.
"Todd has the ability to work well with all across the line, he's not that partisan position. He will work with others to achieve the right goal," he told RNZ.
After he left Parliament as Bolger's staffer, Muller moved into the private sector.
He worked for Zespri in the early 2000s, before moving to kiwifruit and avocado company Apata in 2006, where he was chief executive.
In 2011, Muller move to Auckland to work at Fonterra, where he worked his way up to group director of co-operative affairs.
After Muller left to become an MP in 2014, the co-operative affairs role was taken over by Miles Hurrell – the co-op's now chief executive.
Todd Muller with his wife Michelle last year. Photo / Facebook
Muller was elected as the Bay of Plenty MP by a country mile; his 21,735 votes put him light years ahead of his Labour Party rival, who won just over 6600.
He took the seat over from former Health Minister and National MP Tony Ryall.
As a backbencher, he served on a number of committees, including Māori Affairs, Social Services, and Education and Science.
He was promoted to deputy chair of a number of those committees and held the coveted position of chairman of the Foreign Affairs, Defence and Trade select committee.
Voted against euthanasia and liberalising abortion
Muller is a practising Catholic and voted against both euthanasia and liberalising abortion in the House.
He first began making political waves in Opposition while working on the Zero Carbon Bill.
It was a Government bill, which aimed to develop the framework to reduce New Zealand's net carbon emissions to zero.
National supported the first reading of the bill, after strong behind-the-scenes lobbying from Muller.
It is understood he was well respected on the Government side while ministers negotiated to get the support of National.
Following his work on the bill, Simon Bridges allocated the agriculture portfolio to Muller.
That means he's one of National's main weapons when it comes to wooing rural New Zealand.
National's agriculture spokesman Todd Muller speaking to farmers at a protest outside Parliament in Wellington amid claims the Government was destroying rural New Zealand. Photo / Jason Walls
He's often around the country attending Field Days and A&P shows.
Federated Farmers president Katie Milne told The Country yesterday Muller was "very well-rounded and very well-versed on the issues that we [rural New Zealand] face".
But today he swapped his gumboots and Swanndri for pair of leather shoes and a navy blue suit.
• He was elected to Parliament in 2014, when he was 45, as the Bay of Plenty MP, winning by a substantial margin.
• Before his leadership bid, he was best known for his work on the Zero Carbon Bill, where he worked with the Government.
• Before Parliament, he had a successful career in the agri-business sector – he's had leadership positions at Fonterra and Zespri.
• He has worked in the halls of power before – he was a staffer in former Prime Minister Jim Bolger's office in the mid-90s. In recent days, Bolger has publically supported Muller's leadership bid.
• He is a practising Catholic and voted against both euthanasia and liberalising abortion.
• He is a huge fan of American politics – he went over to the US in 2016 for the Donald Trump campaign.
