This is an updated version of an article first published on Wednesday, May 20.
Bridges confirmed the coup d'état on live TV on Wednesday morning, telling The AM Show two colleagues would be contesting his and deputy Paula Bennett's leadership of the party.
While Bridges wouldn't say at the time who the colleagues were, Muller soon confirmed he was out for the top job, while Kaye was pushing for Bennett's role as deputy.
But at 43rd and 13th respectively on the National Party list at the 2017 election, Muller and Kaye are not exactly high-profile - especially not compared to other potential candidates such as Judith Collins, Mark Mitchell or Amy Adams.
Then again, a once relatively unknown Jacinda Ardern went from 20th-ranked Labour list MP to Prime Minister in less than nine months - so anything's possible.
Who is Todd Muller?
Unfortunately for Muller, he is perhaps best-known to Aotearoa as the "boomer" on the receiving end of Green Party MP Chloe Swarbrick's viral 'OK boomer' wisecrack in Parliament last year.
But while he's the face of a popular millennial internet meme, Te Aroha-born Muller is now also National leader - and that's largely down to his economic nous.
After graduating with a degree in politics and history from Waikato University, he earned immediate experience at the top level of New Zealand politics as a staffer for then-Prime Minister Jim Bolger.
Bolger on Tuesday backed Muller for the party leadership, telling RNZ his significant business experience - which includes stints at executive levels for some of New Zealand's biggest agricultural companies - would help guide the country through the economic carnage caused by the COVID-19 pandemic.
Muller, who has been the MP for Bay of Plenty since the 2014 election, has worked as group director of cooperative affairs for Fonterra, as general manager for kiwifruit exporter Zespri and as CEO of harvest operations firm Apata Ltd.
He has also served on the boards of both the Sustainable Business Council and Plant and Food Research, and as a councillor at Waikato University.
As a result of his expertise, he is a member of the Primary Production Select Committee and was most recently National's spokesperson for agriculture, food safety, forestry and biosecurity.
He has previously served as chair on three select committees - Trade, Defence and Foreign Affairs - and as deputy chair of two, Education and Science.
In his endorsement of Muller, Bolger told RNZ that he "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," Bolger said.
"But going forward the number one issue ... is how do we get economies up growing again, employing people and producing goods. That's really where one has to say Todd's experience has been before he entered Parliament."
Newshub Political Editor Tova O'Brien says Muller is "a good guy" and "super-smart", but isn't sure if he has the ability to tip the election back in National's favour.
"He does have the cred," she told The AM Show on Wednesday. "It is just whether he has that name recognition - he is not this kind of Jacinda Ardern character who can sweep in six weeks out before an election."
Muller said as recently as Tuesday that he had no ambitions to become National leader, telling NZME's The Country that Bridges was "doing a bloody tough job well".
"I do not believe we can sit here now - 130 days out from an election, when we are about to tip into the greatest recession of a generation - [and] make that view that National cannot win."
Just three days later, Muller is now in Bridges' job - marking a significant u-turn.
Who is Nikki Kaye?
Nikki Kaye is better known than Muller for a number of reasons, but of particular significance to the National Party is her history of beating Jacinda Ardern.
In 2011 and 2014, Kaye beat the now-Prime Minister in the Auckland Central electorate, on both occasions inching Ardern to retain the seat she first gained in 2008.
Her campaigns are famous for their grassroots grit - in her first, she reportedly knocked on 10,000 doors to earn an upset win over Labour MP Judith Tizard - and this has seen Kaye remain MP for Auckland Central for more than 11 years.
Her first stint in politics came as a policy researcher for Bill English when he was leader of the Opposition in 2002. She also worked in policy research and a range of other roles in the UK, before returning to Aotearoa in 2007 to contest Auckland Central.
Kaye also has experience as a Cabinet minister. She served as Minister for ACC, Food Safety, Civil Defence and Youth Affairs under Sir John Key's National government between 2013 and 2017, and was Associate Minister of Education and Immigration.
In 2016, however, she was tragically forced to take sick leave following a breast cancer diagnosis. She took several months off to receive treatment and came back in 2017, delivering an emotional speech in Parliament upon her return.
In addition to her political experience, Kaye is also known as an advocate for LGBTQI+ rights and a talented athlete, becoming a regional 3000m running champion in 1997 and the first Cabinet minister to complete the Coast to Coast event in 2013.