Residents of Makerfield are heading to the polls to vote in a contest that will determine the country’s next prime minister.
Labour candidate Andy Burnham has made it clear he will challenge the prime minister if he wins the by-election and returns to parliament.
Speculation about the mayor of Greater Manchester’s leadership bid has been building for months, with many in the Labour Party believing that if he takes the Makerfield seat, it will be a matter of when, not if, he becomes prime minister.
The timescale of his potential premiership depends on several key factors, including which other candidates decide to run in a leadership race.
Here is a look at how quickly Mr Burnham could be installed in No 10:
Quickest
It’s very unlikely, but Mr Burnham could become prime minister in a matter of days.
Once back in Parliament, Mr Burnham would need to trigger an official leadership challenge by obtaining the support of 81 MPs – 20 per cent of the party in the Commons – and from five per cent of constituency Labour Parties (CLPs), or at least three affiliates, including two trade unions.
It is highly likely Mr Burnham would secure nominations quickly, with many MPs already pledging their support.
The contest would then be put to party members and affiliates to vote using a preferential voting system.
However, if Sir Keir decides not to run in the leadership contest - and no other contender comes forward - the vote will not be put to members and Mr Burnham could be crowned in days.
This is unlikely, as the prime minister has repeatedly vowed to fight any contest, while former health secretary Wes Streeting has also made it clear he will be running in a leadership race.
Slower
There may be a scenario where Sir Keir does decide to step down, but not immediately.
This could see him set out a timetable for his departure, perhaps before the Labour Party conference in September, to allow an orderly transition and potential candidates to prepare for a race.
If this happens, and no other candidates decide to run in the race, Mr Burnham could be prime minister within a few weeks.
Slowest
The slowest option would see multiple candidates securing the 81 nominations to run in the race, triggering a full leadership contest.
The timetable is set by the NEC and there is no set time for how long a contest will take, but they usually take several weeks.
The last Labour Party leadership election in 2021, which saw Sir Keir become leader, took around 13 weeks to complete from when it formally began.
In 2016, when Jeremy Corbyn faced a revolt, it took around 13 weeks, while in 2015, the contest was around 18 weeks.
It’s also worth noting that it may take Mr Burnham, or any other candidate, weeks to fire the starting gun on an election, prolonging the process even further.
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