Boris surprised many when he declared himself a Brexiter at the start of the referendum process, as he had been London Mayor and was known to be pro-City, which is pro-EU. So when he declared himself out, many saw it is a political ploy to put himself in Downing Street.
After the result — taking Britain out of the EU — Prime Minister David Cameron announced his resignation, having failed to convince a deeply euroskeptic country to remain inside the union.
It followed another shock announcement from Justice Secretary Michael Gove, who declared he was standing, having fought alongside Johnson to take Britain out of the EU. Gove was widely tipped to not stand, but back Johnson's challenge.
In the end, dramatically, Johnson ruled himself out of running to be the next prime minister, saying:
"Having consulted colleagues and in view of the circumstances in parliament, I have concluded that person cannot be me."
Another candidate who was a forceful voice for the UK leaving the EU is former defense secretary Liam Fox. He has called for party unity following the referendum. Finally, Andrea Leadsom, the former banker and junior minister, who also backed the Leave campaign is also standing.
Home Secretary Theresa May, who backed remaining in the EU, announced she would be standing. She is a political heavyweight and is a favorite among bookkeepers. Stephen Crabb — a rising star — who backed remaining in the EU — is also standing.
So @BorisJohnson has decided not to pull out of contest. Leave vote split between him and Gove and Fox. May looking strongest— Robert Peston (@Peston) June 30, 2016
Thus, the Conservatives have three candidates who backed leaving the EU: Gove, Fox and Leadsom, with two who backed remaining: May and Crabb. Most commentators currently think the final run-off will be between May and Gove.
Not long ago George Osborne, Boris Johnson and Theresa May were favourites to succeed the PM. Only Theresa Remains and is 8/15 at bookies— Lord Ashcroft (@LordAshcroft) June 30, 2016
The next stage is for the Conservative MPs to have a ballot to whittle the list down to two and the final decision will be made by a countrywide poll of all Conservative Party members, with the next prime minister in place by September 9.
Can only feel Boris Johnson will now back Theresa May to beat Michael Gove. He who sticks the knife in last…..— Gary Lineker (@GaryLineker) June 30, 2016
May and Gove are political heavyweights and the final run-off will pit a Remain-backer against a Leave-backer. If Gove wins, he will have the popular mandate for Brexit from the referendum and the backing of his party. If May gets in, she will be in the position of being a pro-EU prime minister, making the decision on how to take forward Britain's relations with the EU.