On 6 March, Ian Warren of Election Data published a poll of the Labour membership. In that poll, 50 per cent of Labour members said that Jeremy Corbyn should step down as leader before the next general election.

This finding will only add fuel to fire of speculation about another leadership election. With potential challengers already jockeying for position, what other lessons can they take from this poll?

1. Understand the membership

Members will be the largest group of voters in the selectorate for the next election, and the polling shows three groups: 36 per cent guaranteed Corbyn voters, 35 per cent ABCs (Anyone But Corbyn) and 29 per cent somewhere in the middle. But don’t let those numbers fool you: the deck is stacked in favour of Jeremy Corbyn.

Swing voters are more likely to favour Corbyn (or another left-wing candidate) by roughly 10 per cent, while 74 per cent of ABCs ‘regularly consider’ resigning their membership. That leaves challengers with just two options: bridging the gap or expanding the selectorate.

2. Growing the pie

Ask any organiser how to win a selection, and they’ll tell you to expand the electorate. When you’re running to be selected as a local councillor, that means printing off a list of members and hitting the phones. When you’re running to be selected as the next leader of the Labour Party, you’ll need to get a bit more creative.

As moderates continue to win the running battle over the party’s structures, rumours of changes to the leadership election process abound. Despite that, the NEC has previously been shy of changing the rules of the game in a way that too clearly undermines the current leader.

That means a future leadership campaign will need a strategy for identifying and signing up as many sympathetic registered supporters as possible. This could even go as far as calling for the cost to be lowered to £1, in line with the French Socialist party’s open primaries that attracted over 2 million voters earlier this year.

3. Principles, not practicalities

Every analysis of the phenomenon of Jeremy Corbyn’s support talks about the appeal of his principles. Every criticism of it, at some point, talks about electability.

Future leadership contenders should pay heed to the numbers: few swing members value moderate totems like “moving the party to the centre” or “understanding what it takes to win an election”. While it’s tempting to dismiss these voters, the evidence suggests that when it comes to Jeremy, the swing voters are there for the movement, not the man.

This is where challengers should focus their energy - people who put a premium on electability are already in the bag. That means showing a bit of passion, having principles, and painting in primary colours on the issues that matter to swing voters. You don’t build (or co-opt) a movement by equivocating.

4. Start banging on about Europe

By the end of this month, the UK will have triggered Article 50. When this happens, the howling and teeth-gnashing of people who are currently (or are ever likely to become) Labour members will be deafening.

A canny contender could turn this to their advantage and position themselves to give voice to the frustrations of these members. Setting out a strong position on Europe pays huge dividends for a leadership campaign - just look at Chuka Umunna's impressive uptick in support across the entire membership.

But pay heed to Owen Smith’s example: just as you can’t have your cake and eat it, and you can’t campaign on your electability and a second referendum too.

5. Keep banging on about Europe

Yes, two sections on Europe. That’s how important it is.

6. Build a team

There’s just one quality in a future leader which swing voters prize more than either of the partisan groups: “unites the Labour Party”. Challengers will need to build support from every wing of the party - not just the usual suspects.

The potential candidates with the most support in this poll are politicians like Yvette Cooper, Keir Starmer and Clive Lewis: those who’ve worked with the Corbyn leadership, but also have their own supporters and their own principles. The idea of a unity ticket will be a powerful one: 50 per cent of swing voters also want an effective opposition to the Conservatives.

7. Take on the media

Unsurprisingly for anyone who’s used the internet recently, parts of the Labour membership aren’t all that keen on the mainstream media. 73 per cent of Labour members say that they don’t trust the media as whole, and the response within the party to politicians taking on the media has been overwhelmingly positive.

Corbyn’s team recognised this, and planned an abortive Trump-esque anti-media reboot earlier this year. Future leadership contenders should revisit this strategy, though perhaps without the “telling everyone first” bit.

8. It’s all in the join date

Finally, forget Cambridge Analytica, the quickest way to work out someone’s vote in a Labour leadership race is when they joined.

With pre-2015 members making up just 20 per cent of the membership, and a firmly decided 20 per cent at that, the main battle is over disaffected former Corbyn voters and post-referendum joiners. "Former Corbynites" tend to have joined after the general election but before Jeremy was elected, and place a particular emphasis on providing an effective opposition to the Tories, while post-referendum joiners want their leader to be in touch with ordinary people.

Future campaigns should then use the latest polling techniques to work out not just what matters most to different groups, but whether or not it would actually change their vote. Next, road test these ideas on Facebook with the people who will decide the election, and hone the message down into battle-tested lines that are proven to move opinion.

With special thanks to Ian Warren of Election Data and Laurence Janta-Lipinski