Rishi Sunak is expected to be confirmed as the new leader of the UK Conservative Party and British prime minister later today.
It comes hours after Boris Johnson pulled out of the leadership race, after securing the the public backing of 59 party MPs - far short of the 100 required to be included on the ballot.
His withdrawal leaves the path open for Sunak, who has around 150 backers - a significant lead over rival Penny Mordaunt, who has 25.
If both of them secure support from at least 100 MPs by Monday afternoon, Conservative Party members will have the chance to vote for their preferred candidate.
However if Mr Sunak is the only one to reach this threshold, he will automatically become the UK's third prime minister this year.
In a statement, Mr Johnson claimed he had "cleared the very high hurdle of 102 nominations", but came to the conclusion that "this is simply not the right time".
Mr Johnson also said there was a "very good chance" he could have been back in 10 Downing Street by the end of the week if he had stood.
However, he said he had "reached out" to leadership rivals Mr Sunak and Ms Mordaunt to see if they could work together in the national interest, but it had not proved possible.
Mr Johnson added that although he was "attracted" to run because of the support from his colleagues, "you can't govern effectively unless you have a united party in parliament".
In response, Mr Sunak tweeted: "Although he has decided not to run for PM again, I truly hope he continues to contribute to public life at home and abroad."
2/ Although he has decided not to run for PM again, I truly hope he continues to contribute to public life at home and abroad.
— Rishi Sunak (@RishiSunak) October 23, 2022
On Sunday, several long-time allies of Mr Johnson - including Britain's Minister of State for Northern Ireland Steve Baker - threw their support behind Mr Sunak.
Mr Baker had warned that a potential comeback by Mr Johnson would be a "guaranteed disaster".
"He's undoubtedly a wonderful man", Mr Baker said.
"I'm afraid, whatever people would like to be true, we need to just ruthlessly face the truth as it is, and the truth as it is is when that vote comes, which it will, his premiership would implode.
"This country cannot afford to be back here in a couple of months."
Me Baker added: "There's a lot of love out there for Boris Johnson. I respect that.
"I'm a big fan of Boris Johnson, but this isn't the time for Boris's style.
"I'm afraid the trouble is, because of the privilege's vote, Boris would be a guaranteed disaster."
How the vote will work
It will be announced by the 1922 Committee who has made it onto the ballot. Hopefuls will need to have secured the backing of more than 100 UK MPs.
If only one of them meets this threshold, they will automatically become UK prime minister.
If more than one candidate remains in the race, they will take part in a hustings in British parliament.
This will be an opportunity for contenders to make their case to MPs, who will then vote in a secret ballot.
If it is required, the result of the first MPs' ballot will be published at 6pm.
Should two candidates still be in the race, it will show the level of support for each candidate in the parliamentary party.
If there are still two candidates in the race after Tuesday, the membership will vote for the next party leader online.
The result will be announced on Friday.
Reporting by: IRN