Robert Peston: What is Lisa Nandy's claim to be Labour leader?

Given that Labour has just faced its worst electoral defeat arguably since 1935, it always looked odd - and dangerous for the Opposition - that the final run-off might have been between two candidates, Sir Keir Starmer and Rebecca Long-Bailey, whose hands were well and truly in the blood of that disaster, as part of Jeremy Corbyn's shadow cabinet.

So the decision of the big GMB union to endorse Lisa Nandy will make for a more interesting contest and a proper choice for Labour members.

Nandy's most important claim on the leadership is she is the only candidate to have argued as a backbencher that Labour should have worked seriously to agree a Brexit deal with ex-PM Theresa May.

It is highly likely that had Corbyn achieved such a deal, the Tory Party would have torn itself apart - creating conditions in which Labour might even have won a subsequent election.

And if May's Brexit had been agreed, the rupture with the EU would have been less severe than BorisJohnson's is expected to be - which would have served the interests of manufacturers and their unionised employees.

So Nandy has proved her ability to think strategically, and in respect of the biggest issue of our times.

She also, in securing GMB backing, has shown she can play the political game; that she understands politics is about backroom deals as well as ideals.

A bit like Starmer, she has been planning her tilt at the leadership in a quiet way for much longer than was widely known.

As I understand it, she would never have entered the race if not hopeful she would get the backing of the GMB - which ultimately turned out to be well founded.

To be clear, that's the big difference between Nandy and Phillips - who is normally a superb public performer, but who did not organise early enough or effectively enough, and who (counter-intuitively) never took the policy risks that might have differentiated her from the rest.

It means Labour's members will probably face a choice between a young left-winger, Long-Bailey who is still loyal to Corbyn, a world-class technocrat in Starmer, who lost the argument that the UK should remain in the EU, and a left-wing voice in Nandy who always eschewed the cult of Corbyn, and whose personal and Brexit history provides some kind of connection with the voters in the midlands and north just snatched by Johnson from Labour.

All the signs are that those members will choose the candidate, Starmer, whose sex, background and ethnicity mean he could have been leader at any point in the party's history. But at least they now have options.