Liz Truss’s resignation after her short-lived tenure as British prime minister has left a vacancy for the top job in government.
Here's a look at the possible runners and riders for the next Tory leader.
Mr Sunak was defeated by Ms Truss in the race to become the new prime minister last month, gathering 60,399 votes to her 81,326.
He was Chancellor of the Exchequer until July 5 when he quit in protest at Boris Johnson’s leadership.
In the last leadership campaign, he positioned himself as the candidate prepared to tell hard truths about the state of the public finances rather than “comforting fairy tales”.
Tory MP Steve Double said his party should unite behind a candidate such as Mr Sunak.
Speaking before Ms Truss announced her resignation, Mr Double said: “Rishi Sunak’s predictions about the disastrous consequences of Liz Truss’s policies have been proven right. We now need someone like him to step up to show that they can get a grip on the situation and lead from the front.”
He added that he was “willing to get behind anyone who will provide the leadership we need, is up to the job and will get back to delivering on the 2019 manifesto we were elected on”.
Penny Mordaunt, leader of the house of commons, said she would “keep calm and carry on” and encouraged others to do the same, in the wake of Truss' resignation.
A former trade minister, with cabinet experience in the defence and international development briefs, she ran to replace Boris Johnson with the catchy campaign name PM 4 PM.
In that campaign, Ms Mordaunt said leadership “needs to become a little less about the leader and a lot more about the ship”.
She came third, narrowly missing out on a place in the head-to-head phase, in which she backed Ms Truss over Mr Sunak.
Could the former Prime Minister return to power in 10 Downing Street?
Just a few hours before Ms Truss’ resignation announcement, close Johnson ally Nadine Dorries tweeted her support for him.
She wrote: “One person was elected by the British public with a manifesto and a mandate until January ‘25. If Liz Truss is no longer PM there can be no coronation of previously failed candidates. MPs must demand return of @BorisJohnson – if not it has to be leadership election or a GE.”
One person was elected by the British public with a manifesto and a mandate until January ‘25.— Rt Hon Nadine Dorries MP (@NadineDorries) October 20, 2022
If Liz Truss is no longer PM there can be no coronation of previously failed candidates.
MPs must demand return of @BorisJohnson - if not it has to be leadership election or a GE.
Mr Johnson very reluctantly left Downing Street, saying in a speech in July outside the famous black door: “I want you to know how sad I am to be giving up the best job in the world, but them’s the breaks.”
He told how he had been unsuccessful in trying to persuade his colleagues that it would be “eccentric to change governments” back in the summer.
The former equalities minister ran in the summer leadership contest, saying she wanted lower taxes and “limited government” that focuses on the essentials.
She appeared to be targeting the anti-woke vote, complaining about “the shutting down of debate” and stressing the need to “reinvigorate the case for free speech”.
The ex-chancellor and health secretary ran under the campaign name “Team Saj” over the summer, saying he would scrap the National Insurance rise and pledging to cut corporation tax to 15%.
Ahead of Ms Truss’ resignation, Downing Street declined to deny reports that she had authorised briefings against Mr Javid and Michael Gove.
Over the weekend, a Downing Street source described Mr Javid as “shit” to a newspaper as they dismissed suggestions Ms Truss had considered him to be her replacement chancellor.
On Thursday, the Ms Truss’ official spokesman told reporters: “You know the Prime Minister takes this very seriously. She thinks it’s very important to treat Parliamentary colleagues courteously.”
The official added that Ms Truss worked for years with Mr Javid and Mr Gove and has “deep respect” for them.
But he did not refute a Times report that she authorised one of her closest aides to accuse Mr Gove of being a “sadist”.
British defence secretary Ben Wallace is a popular figure within the party but has previously insisted he wants to remain in his current job.
Mr Wallace, who has been touted as a possible Tory leader and prime minister, said he wanted people to “stop playing political parlour games”.
He told theearlier this week: “The public wants stability and security and if the government fails to deliver that then they will send us into opposition.”
Asked if he wanted to be prime minister at that stage, he said: “I want to be the Secretary of State for Defence until I finish. I love the job I do and we have more to do. I want the Prime Minister to be the Prime Minister and I want to do this job.”
She resigned as British home secretary just a day ahead of Ms Truss’ resignation, with a scathing letter, lashing out at the PM’s “tumultuous” premiership and accusing the government of “breaking key pledges” including on immigration policy.
Ms Braverman, a former Attorney General, ran in the last leadership race to replace Mr Johnson, promising “rapid and large tax cuts”, and saying she would suspend net-zero targets to deal with the energy crisis and pull the UK out of the European Convention on Human Rights.
He was appointed home secretary in the wake of Ms Braverman’s resignation on Wednesday. Mr Shapps was transport secretary during the pandemic and ran in the last leadership election under the banner “Back Shapps”.
He was among the candidates promising tax cuts, saying he would take 1p off income tax and scrap the proposed increase in corporation tax. He also highlighted his record as a campaigner and organiser to tell nervous Tory MPs “I can help you win your seat”.
The education secretary has been a long-time ally of Mr Johnson. On his appointment to the Cabinet in early September, he became the ninth education secretary in the past 12 years.
Speaking just before Ms Truss’s resignation, Mr Malthouse declined to answer questions about her future as he arrived for a meeting in Whitehall.
Asked if it was all over for Liz Truss as he entered the Cabinet Office he said: “I’m going in to talk about schools.”
The Chancellor – a former health secretary and foreign secretary – returned to the Cabinet in a shock appointment last week when Kwasi Kwarteng was sacked.
But soon after Ms Truss’s resignation on Thursday, allies of Mr Hunt said he would not be standing for the Tory leadership.
The former Cabinet minister will not stand for the Tory leadership, allies said.