London: Liz Truss, who resigned on Thursday, became the shortest-serving British Prime Minister with a tenure lasting for only 45 days.

Speaking outside Downing Street, Truss said she had delivered her resignation to King Charles after meeting with Graham Brady, the leader of the Conservative Party’s 1922 Committee, earlier Thursday.

“Given the situation, I cannot deliver the mandate on which I was elected by the Conservative Party,” she said in a brief speech Thursday afternoon.

Truss said she will remain in place as caretaker prime minister until a successor is named, with a leadership contest expected to take place over the next week.

Here are the main contenders for the top job:

Rishi Sunak

Rishi Sunak, Britain’s former finance minister and Truss’ main opponent in this year’s Conservative Party leadership race, is now seen as a favorite to replace her.

He warned his rival that her tax-cutting plans would send the economy into free fall, accusing her of “fairytale economics” as she promised unfunded tax cuts.

Despite losing to Truss in the final round of voting by Tory members, he was the top choice among party MPs and is considered a safe pair of fiscal hands.

Following the fallout from the mini-budget, supporters of Mr Sunak believe he has been vindicated. One MP who supported him in the leadership race told the Telegraph: “Everything he said has come to pass.”

Penny Mordaunt

Former Defense Secretary Penny Mordaunt surged to prominence during the summer’s leadership race, before finishing in third place to Truss and Sunak.

Broadly seen as a consensus candidate, Mordaunt was second to Sunak in MP voting until the final round of the race, and has since maintained links with Tory MPs in her current role as leader of the House of Commons.

The 49-year-old also escaped largely unscathed from the controversy surrounding Johnson’s departure, and has since demonstrated her leadership prowess in the chaotic early weeks of Truss’ premiership, reports CNBC.

Boris Johnson

Just three months after being ousted from office, some Tory MPs have suggested that former PM Boris Johnson could return to the top job.

Former culture secretary and close Johnson ally Nadine Dorries tweeted Thursday that he was the only MP with “a mandate from party members and the British public,” having won the 2019 General Election.

According to the CNBC report, Johnson previously enjoyed high levels of popularity until losing credibility in the final months of his premiership amid political scandal around Covid-19 rule-breaking and his links to disgraced MP Chris Pincher.