Johnson is by far the most popular candidate among Conservative members and will probably win a leadership contest if he makes the final two.
According to a recent YouGov poll, 39% of Tory members want Johnson to be the next leader, with second-placed Dominic Raab trailing on 13%.
While there are a sizeable number of MPs who are opposed to Johnson, there appears to be a growing view — even among the moderate wing of the party — that he could be the person to unite the party and rescue its disastrous poll ratings, which have plummeted in recent months.
He looks almost certain to make the final two, with the backing of influential MPs from across the party including Johnny Mercer, Jacob Rees-Mogg, and Gavin Williamson.
He would likely claim he is willing to embrace a no-deal Brexit — a policy which is popular with rank-and-file Tory members and probably required for any candidate to win the leadership.
However, a bruising leadership contest could hurt his chances, with his patchy track record in office likely to come under severe scrutiny.
Many colleagues believe he has placed his personal ambition above all principles. As Mayor of London, he championed a liberal, pro-immigration philosophy to a receptive electorate.
When he became MP for Uxbridge & South Ruislip in 2015, he decided to tack right and his been drifting in that direction ever since, a move which has endeared him to the Tory membership, which is typically more right wing than the average Conservative voter.
He last year compared the appearance of Muslim women wearing burkas to "letter-boxes" and refused to apologise.
His decision to back Brexit in 2016 — widely credited as swinging the referendum decisively in Leave's favour — came as a surprise to then-Prime Minister David Cameron, who believed Johnson had made the decision purely on personal ambition.
Then there is his record as Foreign Secretary.Former colleagues say that he was unwilling to read up on policy documents and he made an extensive series of gaffes which caused international diplomatic incidents. He was condemned for saying the war-torn Libya city of Sirte could be the new Dubai before adding: "all they have to do is clear the dead bodies away."