That would be a strange assumption to make.
If he can take seats away from conservatives in an atmosphere where the media is punching at him constantly from the front, while his MPs stab at him constantly from the back.......
The assumption should actually now be that with more support from within his party, and a renewed, more respected outlook being portrayed from outside it, along with the vindication of the relevance of left wing policies in the UK, there is still a lot more to come.
Also, the conservatives have been absolutely shambolic with failed budget after failed budget, Brexit causing a mess and now this a week before negotiations. They have lost all the trustworthiness they exuded and used to use to batter Labour with.