Keir Starmer is on course to win the Labour leadership election by a heavy margin, according to the first YouGov poll of Labour Party members. YouGov – which is the only British pollster to reliably and regularly poll party members, having accurately predicted the outcome of every internal party contest since its foundation – shows Starmer with a first-round lead that would increase over every round of voting, eventually defeating Rebecca Long-Bailey, the shadow business secretary, in the final round.

The first round figures are as follows: Keir Starmer 31 per cent, Rebecca Long-Bailey 20 per cent, Jess Phillips 11 per cent, Yvette Cooper 7 per cent, Clive Lewis 7 per cent, Emily Thornberry 6 per cent, and Lisa Nandy 5 per cent.

This poll looks about right to me as things stand

It would be highly surprising, given YouGov’s record in predicting these contests, if their polls turn out to be off this time. Added to that, it accords with my conversations with Labour Party members throughout the country and, less usefully, my own sense of the contest. As I wrote when Starmer announced he was considering a run, his opening bid was pretty much pitch-perfect (at least as far as my understanding and impression of what Labour Party members prioritise goes).

In addition, he’s been helped by the fact that thus far, none of his big-name challengers bar one – more on that definition below – have performed that well. Long-Bailey’s opening pitch – an article for the Guardian – didn’t say very much. More importantly, it said nothing at all that Starmer did not. It’s in Starmer’s interests for this to be a contest without much in the way that differentiates him from Long-Bailey on policy questions because, bluntly, he fits the description of 23 of the 25 people to have been prime minister and if the contest is simply “who’s the best face for Labour” then he is well-placed to win it.

But the contest has three months to run, and we don’t know much about it yet

Elections are determined by what voters decide the question is – but that question is shaped by the field of candidates in its entirety. Andy Burnham was well-placed to win a Labour leadership race against Yvette Cooper – the contest many expected to take place after the 2015 election throughout Ed Miliband’s leadership – but he struggled in a contest which seemed to offer Labour members a choice between Jeremy Corbyn and three fungible candidates.

The route to the ballot itself is complex, and to my eyes, there are just two candidates with a nailed-on route to it: Starmer is one and Long-Bailey is the other. Does that help Starmer by turning it into a question of performance, or harm him by making it one of ideology? Have Labour members decided they want a breach in terms of ideology in any case? What do Labour members make of the 2019 election?

This is a longwinded way of saying: we know that Starmer is on course to win an election in which all of the thus-far declared candidates make it to the ballot. This is highly unlikely to happen: in fact I’d go so far as to say it is impossible that all of the declared candidates will make it to the ballot.

Would a race between Keir Starmer, Lisa Nandy and Rebecca Long-Bailey be dominated by questions about whether it is time for a woman, or if an MP from a London constituency cannot win back the small towns Labour lost in 2019? (I’m not adjudicating on whether these are good questions: I’m just saying that they are questions that could change the shape of the contest)

And the candidates aren’t that well known

One of the many, many errors that people make in reporting the Labour Party rank and file is imagining that it is a hyper-engaged and incredibly online group of people. This is not the case. The average Labour member is a socially concerned person who gets their news via the Guardian’s website and the BBC. They are also not particularly factional: Momentum, the organisation that grew out of Corbyn’s first leadership election, is the largest factional organisation in Labour politics by some distance: but only one around one in every ten Labour Party members is a Momentum member.

The moment when Jeremy Corbyn sealed the deal with Labour members in 2015 was not on Twitter, or even on Facebook. It was in the first televised debate of the race. That was when, according to the private polling I obtained at the time, he first opened up a lead among Labour members.

This is just supposition based on anecdote, but my impression is that there are five candidates in this contest who are well-known and about whom Labour members have strong opinions: Keir Starmer, Rebecca Long-Bailey, Yvette Cooper, Jess Phillips and Emily Thornberry. These candidates have the least room to grow – I’m not saying it is impossible for them to improve their standing among Labour Party members, but they are the ones who are competing against strongly held preconceptions about them.

Opinions about Lisa Nandy and Clive Lewis are for the most part up for grabs and therefore they could do much better than suggested by these polls – if they get onto the ballot, which is not certain for either.

And we don’t know what the rules of this contest will exactly be, and how fair they will be

The Labour Party has a democratic constitution but it doesn’t have a democratic culture. Internal elections tend to be “free” but they often aren’t “fair”. One reason why Labour’s ruling national executive committee favoured a long contest in 2010 was that some thought it would allow time for a challenger to David Miliband, the frontrunner, to emerge. In 2016, Jeremy Corbyn came within two votes of having to seek fresh nominations to stand again – nominations that might not have been forthcoming, bringing his leadership to an early end.

So we should expect dirty tricks of one sort or another: with the potential to change the result.

I wouldn’t be shocked if Jeremy Corbyn decided to endorse someone

Just because there is an unwritten convention that the departing leader doesn’t endorse a candidate doesn’t mean it will hold. And that endorsement has the potential to transform the race.