A month after one of the heaviest defeats in its history, the Labour party is on its way to electing a new leader. Clive Lewis and Emily Thornberry have until Monday afternoon to win the support they need from MPs to join Keir Starmer, Rebecca Long-Bailey, Lisa Nandy and Jess Phillips in the contest’s second stage. This involves nominations from constituency parties, unions and affiliates, with members and supporters making the final selection and the winner due to be announced at a special conference in April.

Questions about the future of Corbynism are at the forefront, with the socialist ticket of Ms Long-Bailey and Angela Rayner, who wants to be deputy, facing a strong soft-left challenge from Mr Starmer. How the party develops its policies following December’s drubbing is hugely important, and not just for Labour. Given the new government’s programme and Boris Johnson’s character, individual credibility is a key factor: Labour knows it needs a leader who can hold the Conservatives to account. Geography and identity are crucial themes, with no easy answers to the problems thrown up by the growing divide between cities and towns, young and old, England and Scotland. Nor can the characteristics and backgrounds of the candidates be set aside. Unlike the other main UK parties, Labour has never elected a female leader.

The political landscape of the next few years is fraught with risk – including the rise of a far-right party pushing a narrative of betrayal if Brexit turns out to be a disappointment. Under relentless pressure from the news cycle, it is not hard to see why many in Labour are anxious to see the party pull itself together quickly, and put on a brave face for the struggles ahead. But it is essential that the process of reflection about what went wrong under Corbyn is not short-circuited – and that ideas proposed by each of the candidates are explored.

So far, Mr Lewis has done more than the other candidates to advance an analysis of Labour’s problems that goes beyond weaknesses of the manifesto, the leadership and Brexit to address the UK’s political system as a whole. On Sunday he launched a manifesto that included proposals for the democratisation of the BBC and a new body to represent women and girls, as well as plans for devolution, the abolition of the House of Lords and introduction of a proportional voting system (the latter is also supported by Ms Phillips, with the other candidates so far undecided).

A diverse field of candidates and ideas is important, which is why we hope that both Mr Lewis and Ms Thornberry will make it to the next round. In the past, hostility to electoral reform has come from the right and left of the party. Even now, it is unlikely to be the first priority of an opposition facing so many challenges. Nor is it the only policy area in which intellectual work, as well as the community organising that several leadership contenders have described as a priority, is needed. But the problems with first past the post, including the way it perpetuates a Labour-Tory duopoly, shuts out smaller parties and rewards nationalist ones (because votes piled up in one area are easier to convert into seats than those that are thinly spread) can no longer be ignored.

Further constitutional change is inescapable, with plans for devolution to the English regions promised by the Conservatives. Whichever candidates make it through on Monday, Labour’s leadership contest must entail serious discussion of how to shore up Britain’s democratic institutions, and strengthen local decision-making, in an increasingly dangerous world.