Taken back 20 years? He's not done out! Or if you mean within the party then, I wouldn't count shedding a load of backstabbers that don't have any sense of loyalty taking the party back 20 years. I can't tell the difference between them and Tory when it comes to acting on things.
Clearly he has a weak side, but he has shown a strong side too sticking it out through the tough (unlike Cameron). Like Trump he'd be preferable for me to shake things up to get us to turn back onto the right path even though there are downsides. I suspect he'd have a weak stance on immigration though which could be severe considering the strains we're under - technological advancement, economical and social management needs to be ahead of immigration and it's seriously behind at the moment.