Cmon Manny, I'm obviously not suggesting he can't win elections - see the multiple times to both parliament and mayoralty - but that he has historally done very poorly when it comes to the leadership.
And given this byelection is being tret as a proxy leadership election, how the seat is very brexity, how the electorate typically don't like feeling that their vote is inevitable and being taken for granted, how stopping him is a massive scalp for reform greens and lib dems, and how we could well see someone win with less than 30%, I think it's fair to suggest that he wouldn't have stood if he didn't have it in the bag is a tad hubristic.
Which tbh has always been his biggest weakness.