Nominations for Labour's next leader opened at 09:00 BST on Thursday. MPs began formally endorsing candidates to replace Sir Keir Starmer, and Andy Burnham is the only name in the field so far. Labour said it would publish an initial count of nominations around 19:00 the same day.

The rulebook is precise. Labour requires any candidate to get nominations from 81 MPs, and either backing from 32 of the party's 634 constituency branches, or from three of its 31 affiliated socialist societies and trade unions — with at least two of those being unions. Candidates have until the following Wednesday to reach the MP threshold. Labour currently has 326 MPs. If Burnham hits 323 nominations, it becomes mathematically impossible for any rival to assemble the 81 needed to appear on the ballot at all. That would effectively end the contest before ordinary party members got to vote.

The Guardian reported on 20 June that Burnham's allies were confident of an unopposed "coronation," following growing declared support from MPs. The same report noted some Labour MPs felt uneasy about a contest closing before it began, preferring Burnham to win through an actual vote rather than by the numbers alone. Those reservations have not altered how events have unfolded.

Wes Streeting, the former health secretary and the most plausible potential rival, ruled himself out on 22 June. The Guardian said this left Burnham the overwhelming favourite to become leader and prime minister as soon as July. Streeting has since endorsed Burnham directly, as have other potential challengers. Al Carns, the former defence minister who had considered running, ruled himself out on Wednesday evening, just before nominations opened.

Weeks earlier, this contest would have seemed unlikely. Burnham had been out of Parliament for a decade, having left the Commons to become mayor of Greater Manchester — a devolved role outside Westminster. He returned via the Makerfield by-election on 19 June, a result Reuters called decisive for Labour and one that immediately cleared his path to challenge Starmer. Starmer initially vowed to fight any leadership challenge, but announced his resignation within days around 22 June, telling the party he had listened and concluded he was no longer the right person to lead it.

Burnham has signalled continuity rather than change on economic policy. He committed on 29 June to keep the government's existing fiscal rules in place. Asked in late June about an early general election, he said it was too soon to discuss — a carefully measured response that leaves the door open without committing him to anything.

Labour's internal rulebook has been contested for months. The Guardian reported on 14 May that Burnham's backers were already lobbying the National Executive Committee over the contest's rules. One NEC member warned separately against what they called a "Wes Streeting coronation." The irony, weeks on, is that the coronation risk has simply changed names.

The mechanics of the rulebook reflect a genuine tension within Labour. The party's leadership elections are designed to give members and affiliated trade unionists a real say in who leads them. Yet the same rules allow for a contest to close if no rival candidate gathers enough MP support — a possibility that would be perfectly legal but would leave the wider party movement with no vote at all. If Burnham crosses the 323-nomination threshold, he would be declared Labour leader at a party event at the end of the nomination week and would become prime minister on 20 July. Under that scenario, the electorate the party's rules were designed to consult would get no consultation.