Who will replace David Cameron as Prime Minister? The full rundown of favourites in the Tory leadership race

David Cameron’s decision to stand down by October fires the starting gun on a Conservative leadership contest.

MPs must whittle down the contenders to a shortlist of two, who will then be elected as leader by party members, and will become Prime Minister. It will be up to the victorious candidate to decide whether to ask Parliament to back a fresh election.

Here are the contenders:

•​ Boris Johnson

The obvious favourite. He gambled his career on backing Brexit, knowing that a vote to leave the EU would all but guarantee that only a figure from the Out camp could become the next Tory leader. That gamble has paid off today. Popular among the party membership, and one of the most well-known political figures in the country, he is the candidate to beat.

His decision to back Brexit was viewed in many quarters as opportunistic and his willingness to head a campaign which at times appeared to be trashing the Conservative government’s record will mean he has bridges to build with many senior Conservative figures. He will have to be emollient, and non-triumphalist, and perhaps above all, distance himself from Nigel Farage.

• Theresa May

The longest-serving Home Secretary in 100 years took a back seat in the referendum campaign. While backing Remain, she did not hit the campaign trail and delivered only a handful of speeches and interviews, and was critical of many aspects of the EU, particularly the European Convention on Human Rights. Hedging her bets allows her to now emerge as a ‘unity’ candidate, and she is said to have been building up her back-room staff in preparation for a leadership bid.

She has the significant advantage of having served in one of the great offices of state, in a steady and competent manner that has won her many admirers within party and the civil service. At a time of great instability, it may be that she is viewed as steady hand on the tiller. Mrs May does however, lack the ‘star quality’ of a Boris Johnson and party members may doubt her ability to connect with ordinary voters.

• Michael Gove

The Justice Secretary may be able to set himself up as ‘the thinking Tory’s Brexit candidate’. Made an enormous political and personal decision to back Leave, taking on his old friend David Cameron. He performed well during the TV debates, and will be an admired figure among Eurosceptic Conservatives. Along with Johnson, he will be hindered by the fact that he led a very divisive campaign, characterised by ‘blue-on-blue’ action. MPs may also judge that he lacks Boris Johnson’s wider appeal with the electorate. Possibly more likely that he will settle for being his new bosom buddy Boris’s Chancellor.

• Ruth Davidson

The Scottish Conservative leader is a hugely-admired figure, and would offer the Tory party appeal among voters few other candidates could reach. Leading the Conservatives to a second place finish in May’s Scottish parliament elections was an extraordinary achievement for a party that was close to vanishing off the electoral map in Scotland not very many years ago. However, would have to become an MP first, and will be tarnished in the eyes of many Tory MPs and members by her outspoken support for Remain. It may well be too soon for her, but she will have a very influential voice in the debate.

• George Osborne

As Chancellor of the Exchequer, for years considered David Cameron’s natural heir, George Osborne would in ordinary circumstances be top of the list of runners and riders. In today’s circumstances, he only just scrapes in as a contender. His stock among Conservative MPs and members was already falling as a result of a succession of bungles, culminating in a Budget that was overshadowed by the resignation of Iain Duncan Smith and a U-turn over swingeing disability cuts.

He was David Cameron’s right-hand man arguing for Britain to remain an EU member, and attracted furious anger from Eurosceptic Tories after he spearheaded warnings about the economic consequences of Brexit, which were branded ‘Project Fear’, and then proposed a 'Brexit Budget' that was viewed as nothing short of blackmail by many Tory MPs. If he survives the immediate aftermath of the Brexit vote with his job intact, he could be a contender, but his stock is now so low in the Tory party he’ll struggle to make it over the first hurdle.

Outside bets:

• Stephen Crabb

Highly-rated Work and Pensions Secretary, raised on a council estate, so could reach out to non-traditional working class Tory voters.

• Andrea Leadsom

One of the most prominent figures in the Leave campaign, seen to have performed well in TV debates.