Thursday marked the beginning of the second leadership race in three months following the extraordinary resignation of Liz Truss.

Rishi Sunak is the first Conservative MP to receive 100 public endorsements, meeting the nominations criteria for the leadership race.

The news was made shortly before a source close to Boris Johnson stated he had also reached the threshold, but this has not yet been confirmed.

The winner would replace Liz Truss as Britain’s prime minister and become the nation’s third leader in 2018.

By Monday afternoon, by party rules for the leadership challenge, all candidates must have the support of at least 100 Conservative MPs to remain in the race.

This means that a maximum of three individuals can stand.

If three candidates receive 100 endorsements, there will be a vote by MPs, with the top two candidates being presented to the party membership.

If members must vote on the top two candidates, the next leader will be selected by Friday, October 28.

If, however, Tory MPs unite behind one candidate, the battle will be ended by Monday.

The second leadership campaign in three months began on Thursday following the dramatic departure of Ms. Truss, who was pushed from office 44 days into her tenure following a tumultuous few weeks in Westminster during which her tax-cutting mini-budget failed.

Lord Frost, a former minister for Brexit and close associate of Boris Johnson, urged his party colleagues to support Mr. Sunak.

The Conservative peer tweeted: “Boris Johnson will forever be revered as a hero for achieving Brexit.

“However, we must proceed. It is unethical to risk a repetition of the chaos and disarray of the previous year.

“The Conservative Party must support a capable leader who can implement a conservative agenda. That individual is Rishi Sunak.

“As I stated in July, (Rishi) would be an exceptionally competent prime minister. He comprehends the issues, can operate the machine and is a wonderful individual. He would bring about a significant shift in ‘feel’ from the Boris years.’

“That is what we require now. Let’s get behind Rishi.”

Mr. Sunak received the support of his predecessor as chancellor, Sajid Javid, who endorsed Ms. Truss in the previous election and Mr. Johnson in 2019.

Mr. Javid stated that Mr. Sunak possesses the “values our party needs” to “move on from previous mistakes.”

Former minister Johnny Mercer supported him, stating that he could not put himself or his constituents through another Johnson administration given the “awful” lows of the last one.

“Boris is my friend, I adore him, and he’s a fantastic individual, but I don’t think I can put myself through that again. I do not believe I can ask my constituents or my employees to “He stated.

“I adore Boris, and he has incredible talents for this country, but it is time for serious, competent, straightforward, and values-based leadership.”