Boris Johnson and his former finance minister Rishi Sunak are leading the potential contenders to become the UK's next prime minister.

After a monumental, mind-boggling, manic few weeks in British politics, anything could happen... even a Johnson comeback. After Liz Truss stepped down on Thursday, the race is hotting up with candidates canvassing support to become Conservative Party leader in a fast-tracked contest. 

Truss lasted 45 days and those who want to replace her are now scrambling to find the 100 votes from Conservative lawmakers needed to run in a battle which the party hopes will reset its ailing and floundering fortunes.

According to opinion polls, the Conservatives face a wipe-out in the next national election. The race is on to become the fifth UK premier in six years. 

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What happens next and who are the runners and riders?

The first ballot of the 357 Conservative MPs is on Monday. A candidate needs at least 100 backers, meaning the ballot can produce no more than three options. If there is more than one candidate, another ballot among MPs will be later on Monday. If there are three candidates, the one with the least votes is out.

If there are two candidates at the end of the ballots and nobody withdraws after the indicative vote, party members will vote online to decide the winner.

The UK's new Prime Minister will be announced by Friday 28 October. Given the divisions in the party, there is no obvious unifying candidate. 

Who are the potential candidates?

BORIS JOHNSON

What a comeback this would be. Johnson, who left office in July comparing himself to a Roman dictator brought into power twice to fend off crises, might face difficulty in reaching 100 votes after his three-year tenure was blighted by scandals and allegations of misconduct.

One of his former advisers said he was unlikely to reach the target, having alienated dozens of Conservatives during his tumultuous time at the helm. He was forced by his fellow Conservative MPs to step down just three months ago. Some MPs have spoken off the record about resigning from the party, or even forcing by-elections, if Johnson were to regain the leadership.

The British newspaper Financial Times said a Johnson return would be "farcical." A former advisor to Johnson, Will Walden, said: "The country needs a grown-up, serious leader. Boris had his chance, let's move on. I suspect that is not what the Tory party will do, they may well re-elect him."

However, many Tory MPs still see him as a winner. He finally became PM in 2019 and went on to secure a landslide election victory by promising to 'Get Brexit Done,' which he did indeed do by completing the UK's withdrawal from the EU. Business minister Jacob Rees-Mogg said he was backing him, tweeting his support with the hashtag '#Borisorbust.'

RISHI SUNAK

Sunak, the former Goldman Sachs analyst who became finance minister just as the COVID-19 pandemic arrived in Europe and was runner-up to Truss in the previous leadership contest this summer, is the current favorite with bookmakers.

Proven right in his warnings that Truss's fiscal plan threatened the economy, he remains deeply unpopular with some party members after helping to trigger the summer rebellion against Johnson.

He is also seen as a 'safe pair of hands' and with the current market turmoil, he might be seen as the perfect candidate to steady the ship. Some newspapers say he will definitely stand in the leadership contest and some MPs have begun declaring their support for him.

PENNY MORDAUNT

Mordaunt is seen as a clean pair of hands, largely untainted by earlier administrations. But she is also untested and, so far, she is lagging Sunak and Johnson in getting backers.

A former defense minister, Mordaunt was a passionate supporter of leaving the European Union who only just missed out on the final two-place run off in the recent leadership challenge.

Mordaunt spent her time in Truss's government on the inside as Commons leader and won plaudits for her performance in parliament on Monday, when she defended the government even as it reversed most of its policies.

One lawmaker has described Mordaunt as having "broad appeal," referring to her ability to find friends in the various tribes of the party. But despite her rousing personality, some may see her inexperience as a huge risk.

Who will win?

The new prime minister inherits an economy heading for recession, sky-high inflation, rising interest rates, labor shortages and a cost-of-living squeeze. Truss, leader for now, said the decision on pressing ahead with the finance minister's fiscal plan on October 31 will be down to the next PM – who will be appointed just three days earlier.

This decision is crucial to the future of the Conservative party and the careers of its representatives. Whoever gets the job has a mountain to climb to restore or renew the reputation of a party badly trailing in the polls, although it holds a big majority in parliament and need not call a nationwide election for another two years.

On the agenda will be unifying a fractious party, appealing to the electorate, handling a European energy crisis, coping with the Ukraine conflict and re-building the trust of wobbling investors.

After the mayhem in recent weeks and hours, anything is possible. Let the race begin.