This evening Boris Johnson will face a vote of confidence in his leadership of the Conservative party.
The vote will take place between 6pm and 8pm on the evening of 6 June, with the result expected to be announced by Sir Graham Brady, chair of the 1922 committee of backbench Conservatives, shortly afterwards.
The vote was called because more than 15% of Conservative MPs – 54 – have sent letters to Brady saying that they no longer have confidence in Boris Johnson as leader of the party.
The letters are private so we do not know who has sent them or what reasons they give for their decision. However, some have explained publicly why they have decided to call for the vote – many because of the prime minister’s failures to stop lockdown-breaking parties in Downing Street , but some MPs have also criticised other aspects of his government, including a focus on campaigning and rhetoric, and a failure to deal with the big issues facing the UK. 
The vote is a secret ballot, with MPs voting yes or no to the question of whether they have confidence in the prime minister. Because of the suddeness of the vote and the tube strike affecting travel, proxy ballots are being allowed for MPs who cannot make it to Westminster. MPs not present have to indicate in advance who will place their vote for them.
Johnson needs a simple majority (180 of Conservative 359 MPs) to win.
All MPs who have the Conservative whip can vote in the ballot – currently 359. Some of those – between 160 and 170 – make up what is called the ‘payroll vote’. This is the MPs who are government ministers, ministerial aides and other related positions like trade envoys. These MPs are expected to vote with the government on all votes in parliament, though the confidence vote is a secret ballot – there is no way of knowing who has voted for or against the prime minister. Some members of the payroll vote may resign as they intend to vote against the prime minister and do not feel able to remain in their role – John Penrose MP, the prime minister’s anti-corruption tsar, has already done so. 
Only those MPs who have the Conservative whip can vote in the ballot – a number of MPs were elected as Conservatives but lost the whip due to allegations of misconduct. They will not be able to vote.
If Boris Johnson wins the confidence vote, he remains as leader of the party and as prime minister. However, the fact that the vote is happening at all shows how damaged his reputation is with his own MPs.
If the margin of victory is particularly tight, and a large proportion of his party reveal they don’t have confidence in him, then he may find that it becomes even more difficult for him to govern.
In 2018, Theresa May won a confidence vote by 62%-38%, but resigned less than six months later following poor results in the UK’s final European elections.
Press reports  have suggested that if Johnson wins he is planning a ministerial reshuffle to shore up support and reward those who vote for him.
If Johnson loses the vote he would no longer be leader of the Conservative party but he would still be prime minister. Having lost the vote, he would not be allowed to stand in the leadership contest that would automatically be triggered. The 1922 committee would set out a timetable for the election of the new leader – last time, in 2019, it took around two months between Theresa May announcing her resignation and Boris Johnson becoming prime minister.
Johnson could decide to stay on as prime minister while his successor is chosen. Both May and David Cameron did so in 2019 and 2016 respectively, though they both resigned rather than lost a confidence vote.
If Johnson chose to step down as prime minister immediately, this would leave open the question of who would take on the role while the party decided on its new leader. There is no constitutional role for a formal interim or acting prime minister role – anyone taking on the role has all of the powers associated with it. The current deputy prime minister, Dominic Raab, or another senior minister could take over for the duration of the leadership contest, but this would need to be agreed by the Cabinet. Though Raab took on many of the prime minister’s duties in April 2020 when Johnson was in intensive care with Covid, appointing a prime minister expected to govern only for a set period of time would be uncharted territory for the UK.
Under the current rules of the 1922 committee, if he wins this evening the prime minister cannot face a vote of confidence for another 12 months. However, these rules can be changed by the executive of the 1922 committee. According to The House magazine, “there is no codified rulebook for the 1922 committee.”  And the specific process for confidence votes is not publicly available – “it is in Brady’s sole possession.” This means that the committee could change the rules at any time.
The 1922 committee does not have its own website. According to Wikipedia  the committee is led by:
Sir Graham Brady – chair
William Wragg – vice-chair
Nusrat Ghani – vice-chair
Bob Blackman – executive secretary
Gary Sambrook – executive secretary
Sir Geoffrey Clifton-Brown – treasurer
There are also seven executive members.
By comparison, the Labour party rulebook is available online. 
- Neill B, I’ve submitted a no confidence letter in Boris Johnson because we can’t win an election with him in charge, inews, 1 June 2022, https://inews.co.uk/opinion/no-confidence-letter-boris-johnson-submitted-cant-win-election-him-charge-1662256
- See for example letter from Jesse Norman MP, available at https://twitter.com/Jesse_Norman/status/1533699235417403393?s=20&t=4TXpj7ZGiszp5P1_o1eXsg
- See for example https://twitter.com/breeallegretti/status/1533739380027928579?s=20&t=HQomy7JKVrDPqDCuuuYSrg
- Rodgers S, How the process for a confidence vote in the Conservative leader works, The House Magazine, 5 June 2022, https://www.politicshome.com/thehouse/article/how-does-the-confidence-vote
- 1922 Committee, Wikipedia, https://en.wikipedia.org/wiki/1922_Committee#Current_executive_committee
- Available at https://labour.org.uk/wp-content/uploads/2022/03/Rule-Book-2022-a.pdf