Unfortunately (perhaps) Vlad, the only constant winners in First Past The Post electoral systems are those who hold the middle ground. When Labour did allow its left wing to be dominant, under Michael Foot and the Neil Kinnock it was unelectable and spent 18 years in Opposition.
Theresa May is trying to be clever. She identifies the unwashed masses who support Brexit as "middle ground" and is pitching her messages towards them - which is why she has become unstuck over Windrush. But until Labour ditches Corbyn or at least starts to disconnect itself from WRP manque image it has managed to acquire it will be difficult for it to sustain a Parliamentary majority.
The Tories were unelectable for 13 years and Labour saw off three supposed middle ground Conservative leaders and then
the magic wore off. There was nothing intrinsically not middle ground about Milliband indeed his sole keynote policy and attitude to privatised utilities eventually was taken on board by the tories. But I think victory which the polls predicted for Miliband was illusiory because the ukip numbers were high and there was evidence that UKIP potential parliamentary seats would just go Tory.
And
that should have been it for Labour who should have according to the script; meekly accept the Tory narrative that the crisis of 2008 was Labours fault. Each Labour leader who was apologetic about Labour's record could be the successfully and succesively be knocked down.
Corbyn has reversed that and instead entering a period of the middle class vote unable to be mined further. Corbyn found a New constituency in the youth vote.
The new tory approach is to try make people forget about these Corbyn successes, and remember the Toby Young doctrine that Corbyn makes Labour unelectable and those touted as leaders and true Labour are back from a three to two year sabbatical suggesting that public apology and public reflection on their own supposed uselessness is the way back to Government.
Matthew D'Ancona on the new Tory narrative on Corbyn
https://www.theguardian.com/commentisfree/2018/may/06/tories-peak-corbyn-local-election-resultsMatthew Norman on the tedious bubbling up like a fart in the bath of the old New Labour(yes them) narrative on Corbyn.
https://www.independent.co.uk/voices/jeremy-corbyn-local-elections-david-blunkett-labour-a8338961.htmlName one person who can be Corbyn's replacement who has a following in either the party or the Country.
Any problems Labour have lie with an electorate who by a very small majority did a quite stupid and thoughtless thing at the behest of some unscrupulous people. The last thing Labour should be thinking is offering up Corbyn as a pointless superstitious shamanic sacrifice taking on everybodies political sins rather than Offering him as a sensible alternative to the nest of fools which is TORKIP.