[1] Theresa May, then serving as home secretary, won the contest after the withdrawal of Andrea Leadsom, and succeeded Cameron as prime minister on 13 July 2016.

[6] This prompted her to broker a confidence and supply deal with Northern Ireland's Democratic Unionist Party (DUP) to support her minority government.

[7] May's handling of the campaign was widely criticised, particularly the role of her chiefs of staff Nick Timothy and Fiona Hill, who both resigned within days of the result.

[12] After the Grenfell Tower fire in June 2017, May's leadership faced further criticism following her initial refusal to meet victims, and what was described as her poor handling of the crisis.

[15] Andrew Mitchell, an ally of Davis, was said to have told a dinner that May was finished and was said to be organising letters to force May to announce her date of departure.

[16] A July 2017 report in The Independent said a core of fifteen Conservative MPs were ready to sign letters of no confidence, with forty-eight needed to trigger a contest.

[18] She then announced on 31 August 2017 that she intended to stay on to fight the next general election, which under the Fixed-term Parliaments Act 2011 was scheduled to be in 2022, though it could be held earlier.

Many saw this as a way of positioning himself for a leadership challenge, though some commentators such as columnist Iain Dale and Newsnight's political editor Nick Watt argued this was the wrong interpretation and that Johnson's motivation was to assert his influence in Brexit negotiations.

[20][21] The timing of the article—a few days before May was due to give a significant speech on her plans for the UK's relationship with Europe after Brexit, and shortly after a terrorist attack in London—was criticised.

Kimiko de Freytas-Tamura, writing in the New York Times, saw it as an attempt to court an anti-Islamic segment of the Conservative Party membership, who would be the electorate in the final stage of a leadership campaign.

Brexit secretary Dominic Raab and others resigned from the Cabinet in response,[33] with Jacob Rees-Mogg calling for a leadership election for the first time.

Members of the Eurosceptic European Research Group including Rees-Mogg and Baker were seen to be launching a coup in mid-November following the Cabinet resignations.

[40] However, facing likely defeat with opposition from the ERG, DUP and Conservative MPs who had supported Remain during the referendum, the vote in Parliament was delayed to January.

[47] In a speech to Conservative MPs immediately before voting, May said that she did not intend to lead the party into the 2022 general election[48] and that she would seek a legally binding addition to the withdrawal agreement with the EU to address concerns over the Northern Ireland backstop.

[57][58] With one report saying May intended to remain until autumn 2019, further senior Conservatives openly campaigned to replace her, including Andrea Leadsom, Jeremy Hunt, Michael Gove and Sajid Javid.

The 1922 Committee executive considered changing the rules such that four candidates would go to the ballot of the party membership;[68] they also recommended increasing the number of MP nominations required to eight.

In November 2018, following his resignation from the role over a proposed deal on the UK's departure from the European Union, Raab became the bookmakers' favourite to be new leader, followed by Javid or Johnson.

[85] Following a poor result for the party in the 2019 local elections on 2 May 2019, Dominic Raab, Sajid Javid, Michael Gove and Matt Hancock gave speeches and interviews that the journalist Tim Shipman described as a "beauty contest between those jostling to succeed Theresa May".

[86] On 8 May 2019, Andrea Leadsom, the Leader of the House of Commons, stated she was "seriously considering" a second bid for the party leadership.

The former Conservative leader Iain Duncan Smith warned on 30 May that there were too many candidates running and urged the 1922 committee to "accelerate the process".

[102] On 1 June, Liz Truss revealed an article of hers to be published the following day in The Mail on Sunday, providing Johnson with his first endorsement from a Cabinet minister.

[118][119] Before nominations formally opened on 10 June, Johnson promised to cut income tax for higher earners[120] and Gove to reduce VAT.

[124][125] On 13 June, the chancellor Philip Hammond wrote to candidates asking them to restrict themselves in any policy pledges they made to the current 2% of GDP deficit limit.

[134][135] In the early hours of 21 June, police were called to Johnson's home after neighbours heard an altercation between him and his girlfriend Carrie Symonds.

All candidates who had not yet been eliminated would be invited to take part in a hustings debate chaired by Emily Maitlis, followed by a Question Time special with Fiona Bruce.

On the same day, Sky News also announced plans for a head-to-head leadership debate between the final two candidates in front of an audience of Conservative Party members.

[240][non-primary source needed] In anticipation of Johnson's election, a number of ministers had announced that they would resign from office, due to his willingness to leave the EU without a deal.

[246] Devolved administrations expressed a similar tone; Scotland's Nicola Sturgeon questioned his "lack of principle", and pledged to work with other parties to prevent the UK leaving the EU without a deal.

[247] Welsh first minister Mark Drakeford urged "seriousness" and "maturity", and also called for a further referendum if Johnson was unable to pass a deal that commanded the support of the House of Commons.

[249] Dame Carolyn Fairbairn, the director-general of the CBI reacted to the result by urging the new prime minister to secure a deal, to "unlock new investment and confidence in factories and boardrooms across the country".