The race to be the UK's next prime minister began in earnest on Friday, with some senior government ministers throwing their support behind Boris Johnson.
Following Liz Truss' resignation, Johnson reportedly cut short his holiday in the Caribbean, arriving back home on Saturday in a bid to sound out colleagues and assess whether he has enough support to win the Conservative party leadership contest.
Business Secretary and Johnson loyalist Jacob Rees-Mogg were among the dozens of Tory MPs to come out in support of Johnson, with many allies posting on Twitter #BackBoris.
Those seeking to replace Truss — now the shortest-serving PM in UK history — must secure 100 nominations from Conservative MPs by Monday afternoon.
Should just one contender achieve this feat, they will be named PM the very same day. But should two or more contenders emerge, some 170,000 Conservative party members will vote in an online ballot.
A new PM is promised to have been chosen by Friday, 28 October. Whoever wins will be the UK's fifth leader in six years, presiding over a country facing hard times.
But who is in the race?
Sunak is the bookmaker's favourite.
The 42-year-old former treasury chief came second to Truss in the last Conservative leadership race.
During the heated TV debates between the two, Sunak slammed Truss' proposed economic policies of slashing taxes, claiming they were reckless "fairy tales" that would send the economy into free fall.
He positioned himself as a stability candidate who could face up to hard truths about the UK's public finances.
Most of what Sunak predicted came to pass, notably the pound collapsing in value, with some in the Tory party claiming this vindicates his leadership credentials.
Sunak was formerly the Treasury chief under ex-PM Boris Johnson.
He resigned after a succession of scandals hit Johnson's government, particularly over drunken parties in Downing Street during the lockdown, but was blighted by Johnson's demise.
Sunak steered the UK through the coronavirus pandemic, overseeing billions of pounds in government handouts to help businesses and workers hit hard by COVID-19.
Born to Indian parents who moved to the UK from East Africa, Sunak attended the Winchester College private school — which costs £33,990 a year for day pupils — and studied at Oxford.
Some see Sunak as out of touch and an easy target for the opposition amid a cost of living crisis because of his elite education and last jobs at the investment bank Goldman Sachs and a hedge fund.
He was also sharply criticised following revelations that his wife, Akshata Murthy, avoided paying taxes on her overseas income. Her father is one of the richest men in Iran.
Penny Mordaunt is the first candidate to officially confirm her intention to run in the upcoming leadership election. She is currently serving in government as the leader of the House of Commons.
The 49-year-old got bronze in the last Tory leadership race, coming in third behind Sunak and Truss.
Mordaunt did not hold a senior post in Johnson’s Cabinet, allowing her to present herself as a clean break from his scandal-ridden government.
Mordaunt is popular among Conservative MPs.
She has stood in for Truss in recent days, speaking on the ex-PMs behalf after former chancellor Kwasi Kwarteng was sacked for his botched economic plans, which spooked the markets.
At the time, Mordaunt had to deny Truss was hiding "under a desk".
Some Conservatives believe she could be the perfect candidate to help the fractured party, which on Wednesday faced accusations that members were being bullied and manhandled into supporting a parliamentary vote.
Yet Mordaunt is a largely unknown figure amongst ordinary Britons.
Mordaunt played a prominent role in the pro-Brexit campaign. She was the first woman to become British defence secretary in 2019 — though she was removed by Johnson after just three months in the post because she had backed another candidate for party leader, Jeremy Hunt.
Braverman helped catalyse Truss' demise.
She quit as Home Secretary on Wednesday, slamming Truss' “tumultuous” leadership in a fiercely worded resignation letter.
Truss hung up her hat three hours later.
A 42-year-old former barrister whose parents emigrated to the UK from Mauritius and Kenya, Braverman tried — and failed — to replace Johnson in the last leadership race.
During her very brief stint as Home Secretary, Braverman vowed to crack down hard on asylum seekers, saying it was her “dream” to see planes deporting those seeking safety in the UK to Rwanda.
Her speech about this deportation plan — which the UN says is illegal — sparked controversy, which could taint her leadership bid.
Braverman also wants to pull the UK out of the European Convention on Human rights, another divisive topic.
She made headlines — and was mocked by opponents — when she attacked government critics as "the Labour Party, it's the Lib Dems, it's the coalition of chaos, it's the Guardian-reading, tofu-eating wokerati..."