Why is Labour sticking with Jeremy Corbyn?

Question

Labour under Corbyn has already lost two elections, including getting humiliating 13.7% in the European Parliament poll. One of the reasons for such an extremely poor result was Corbyn's confusing position on Brexit. It has changed a bit now, but it's still much more unclear than the positions of the Tories and the LibDems.

It seems that the great majority of Labour MPs are determined to stop no-deal and/or hard Brexit. To do it effectively, they need a leader that can make the party win the election. Why is Labour sticking with the leader who arguably cannot win?

In the current situation, a possible election would become a vote on Brexit. Corbyn is not trustworthy for a large number remainers, who make up a large percentage of Labour's electorate. Moreover, there are a lot of voters who could consider voting Labour, but will never accept Corbyn as a prime minister. Why won't Labour choose someone who would be acceptable as a leader of a cross-party anti-hard-Brexit coalition?

This Guardian opinion piece goes into more details on the above arguments. However, I still haven't found any answer to the question posed in the title: Why is Labour sticking with Jeremy Corbyn?

Update:

@mikado says that Corbyn has support from party membership. But why does he have support? Labour members are overwhelmingly pro-remain, and I can't understand why a remainer would support Corbyn, who 1) is a Brexiteer himself 2) loses election after election and makes hard-Brexiteer Tories more likely to win.

@Dan Scally: "You're seeing things through too much of a brexit veil"

Yes, I understand that a lot of people support Corbyn because of policies not related to Brexit. But right now Brexit is the single most influential event for the future of the UK, and when it's done, it will be something that nearly impossible to change for a long time. Is nobody in Labour thinking strategically? I mean something like "let's choose some centrist for now, so that we can easily join forces with the LibDems and others, and when we're done with the problem of Brexit we can choose Corbyn or another left-winger".

Answer 1

I'm guessing it has everything to do with the power structure of the Labour party. For example, Wikipedia says

A vote of no confidence in Corbyn was made by the parliamentary party on 28 June [2016], with Corbyn losing the vote by 172 to 40, with four spoiled ballots and thirteen absentees. However Labour Party rules did not require Corbyn to resign as a result of the vote.

And the article cited for that has Corbyn statement in the aftermath

“I was democratically elected leader of our party for a new kind of politics by 60% of Labour members and supporters, and I will not betray them by resigning. Today’s vote by MPs has no constitutional legitimacy,” he said.

There was however a leadership election again in September 2016, which Corbyn also won:

Corbyn was re-elected as Labour leader on 24 September [2016], with 313,209 votes (61.8%) compared to 193,229 (38.2%) for Smith – a slightly increased share of the vote compared to his election in 2015, when he won 59%. On a turnout of 77.6%, Corbyn won the support of 59% of party members, 70% of registered supporters and 60% of affiliated supporters.

So if that is any indication, Corbyn will stay on as leader until deposed by a similarly broad vote of the party base. I don't know enough of the details of the Labour party internals to tell you what needs to happen for such a vote. (I guess that would be a good separate question.)

I'm not sure how often party-level leadership is polled by UK pollsters, but in 2017 there was one

A majority of people who voted Labour at the last general election want Jeremy Corbyn to stand down as party leader, a new poll has found.

Fifty-four per cent of people who backed the party in 2017 want him to resign, according to a YouGov survey, while only 29 per cent want him to stay in the post.

Clearly Corbyn didn't care to resign because of that. It might be because the same poll found that

However, he is likely to take comfort from the fact that he remains popular among people who plan to vote Labour at the next election. Fifty-four per cent of this group want him to stay in post, while 34 per cent think he should quit.

Yougov which tracks his popularity puts him as the 1st choice of Millenials, but far lower for other age groups.

It's hard to say what Corbyn may be thinking/hoping, but perhaps he hopes that post-Brexit things will return to a "normal" left-right divide in UK politics, and Labour might get those voters back. Whether that is realistic or not, time will tell.

In the leftist wing of the party (which seems dominant within the party now), the narrative seems to be that they'll pull off another surprise election result in the next general election, like they did in 2017, and that Corbyn should only resign if Labour loses heavily in the next general election.

Another leadership challenge from the Labour right, like Owen Smith’s in 2016, was certain to be a failure. The Labour membership believed that the 2017 general election had vindicated their decision to keep Corbyn in his place the previous year. Even if the polling figures for Labour were looking bad — which wasn’t the case until the past few months — they could still point to the dramatic turnaround over the course of the last campaign as reason to keep faith with Corbyn. Only a heavy defeat for Labour in a fresh election was likely to change things.

They also say that Corbyn has given up enough ground on Brexit (on the prospect of a 2nd referendum), much more so than the Conservatives have, and consequently that the "hard Remainers" are simply ungrateful. They also point out that Formby's "Composite 13", which asked for Labour to "campaign energetically" to stay in the EU lost out at the party conference in September. And they interpret that as a vote for Corbyn.

Answer 2

Corbyn did remarkably well at the last election, making up huge ground against the Tories. Therefore going in to another election he seems like a good bet, as he has a proven track record when it comes to campaigning.

Secondly changing leader so close to an election is almost always a mistake. Selecting a new leader takes weeks in the best of circumstances and Labour probably doesn't have that long before the next election campaign starts. Whoever takes over will be relatively known to the electorate too, and it looks bad to have just changed and be going into an election with the manifesto of the last guy (i.e. Corbyn) because you didn't have time to write your own.