He'd be slaughtered as a putin enabler and be front page on all the scum tabloids stomping on Ukraine with the tagline, 'uk citizens next'. Nothing puts a fire under the arses of the thick as pig spit* racist knob head vote like project fear. From being a commie one day, he'd be a nazi the next and the easily governed would swallow every penny of it. The hatred of a principled man is that he can't be bought off or talked round, so they found his hot topic, nuclear weapons and pursued him as a national weakness. The thick twits* of the uk gobbled it up and wanted seconds. Net benefactor boris 'kin johnson.Honestly, I'm not sure. If you took the country as it is, and have the Johnson>Truss>Sunak mess play out exactly as it did to ensure the same view of the Tories, I still think that the attack lines against Corbyn would make it competitive. The big question would be whether Reform would be playing so much of a spoiler role or whether the dislike of Corbyn would see them a bit less attractive for a lot of Tory voters.
I'd guess he probably would win, but it would be a tight victory with a small majority. This would probably end up badly for Labour as the party would be fractious under his leadership and he might struggle to do anything meaningful.
It is an interesting question though and a reminder of just how important timing is in politics - if Starmer had toppled Corbyn after 2017 and then lost badly to Johnson in 2019, he'd likely be gone already and who knows what Labour would look like now.
And oh how they cried for their queen. Morons.