Corbs is certainly riding high on a populist tide.
When does the backlash begin?
They have tried everything since he became an MP in the 1980s. That doesn't mean they will not stop at anything to discredit him. Maybe, a 1920s Daily Mail Zinoviev letter type, that was used to discredit the Labour Party, will appear to show how Corbyn/ McDonnell are really a front for Putin and are behind all the cyber attacks.
In a way sections of the establishment has thrown a lot at him. However, it has been interesting that the CBI and the City of London have been/still are very very quiet about Labour's economic policies. Which may suggest they are looking at Labour as a very credible alternative to the mess economically, socially and politically the Tories are in.
There is nothing like uncertainty to concentrate the minds of the ruling class to try and find a 'solution' to problems. A large section of the country are angry and demanding radical change, hence the vote for Corbyn. Brexit is a mess and they are concerned about what the outcome will be and how it will affect them. They look at the Tories and see what we all see, people completely out of their depth, who don't know their backsides from their elbows. They appear like they can't negotiate their way out of a room, never mind with the EU. The alliance with the DUP makes some very nervous.
I don't doubt there will be an attempt at a backlash. And all this call for a 'national grand coalition' led by the likes of the Blairites around Benn, to deal with Brexit and to bail the Tories out of the brown stuff, is part of trying to keep Corbyn out.