After Boris Johnson’s dramatic exit from the Conservative leadership contest on Sunday night, we may know who the next UK prime minister will be by 2pm, even before. Or we might not know until Friday. Here is how it could pan out. What is the first stage today? By 2pm on Monday, any would-be candidates will have to submit at least 100 nominations from Conservative MPs. Rishi Sunak will manage that easily, with about 160 or so MPs publicly signed up. Boris Johnson will not, hence his departure from the race on Sunday evening. Penny Mordaunt is still on about 30 public votes, but could get some support from MPs who backed Johnson. Could we get a new Conservative leader today? Yes. This would happen shortly after 2pm if it is announced by Sir Graham Brady, the chair of the 1922 Committee of backbench Tories, that only Sunak has reached the threshold. We might even find out before 2pm, if Mordaunt realises she will not get to 100 and the Commons leader decides, like Johnson, to withdraw. What happens if two people get 100 nominations? If that happens, we get into the second stage of the process. There would be a private hustings for MPs at about 2.30pm, and MPs would hold a vote on the candidates. This was planned so that if three had made the 100-vote threshold, the candidate who came bottom in the vote would be eliminated. What would happen after that? With a two-person MPs’ vote, there is no compulsion for the loser to drop out, although if the margin was huge, for example about 240 MPs to 110, there would be significant political pressure for the bottom-placed runner – in this case almost certainly Mordaunt – to cede. But if she did not, the process would go to an online vote of Tory members, closing at 11am this Friday, with the winner announced soon afterwards. When would a winner become prime minister? Most likely a day or so after the result, although there is nothing constitutionally firm about this. If Sunak is crowned on Monday, Truss might visit Buckingham Palace to resign on Tuesday, with Sunak following shortly after to see the king. A Friday result might slow things down a touch, given the weekend.